Narimane Lammari

Ouahida Louaer

Abdeslam Hassen Meniai

Hatem Fessi

Abdelhamid Elaissari
email: abdelhamid.elaissari@univ-lyon1.fr

Plant oils: From chemical composition to encapsulated form use

Keywords: Polymeric nanoparticles, SLN: Solid lipid nanoparticles, EE%: Encapsulation efficiency, HLB: Hydrophilic lipophilic balance, SUV: Small unilamellar vesicles, LUV: Large unilamellar vesicles, MLV: Multilamellar vesicles, NLC: Nanostructured lipid carriers, MIC: Minimum inhibitory concentration, AUC: Area Essential oil, vegetable oil, encapsulation, polymeric nanoparticle, liposome, solid lipid nanoparticle. Graphical

The last decade has witnessed a burgeoning global movement towards essential and vegetable oils in the food, agriculture, pharmaceutical, cosmetic, and textile industries thanks to their natural and safe status, broad acceptance by consumers, and versatile functional properties. However, efforts to develop new therapy or functional agents based on plant oils have met with challenges of limited stability and/or reduced efficacy. As a result, there has been increased research interest in the encapsulation of plant oils, whereby the nanocarriers serve as barrier between plant oils and the environment and control oil release leading to improved efficacy, reduced toxicity and enhanced patient compliance and convenience. In this review, special concern has been addressed to the encapsulation of essential and vegetable oils in three types of nanocarriers: polymeric nanoparticles, liposomes and solid lipid nanoparticles. First, the chemical composition of essential and vegetable oils was handled. Moreover, we gather together the research findings reported by the literature regarding the different techniques used to generate these nanocarriers with their significant findings. Finally, differences and similarities between these nanocarriers are discussed, along with current and future applications that are warranted by their structures and properties.

Introduction

The last decade has evidently witnessed a tremendous surge in the use of herbal medicine as a form of complementary or replacement therapy [START_REF] Mainardi | Complementary and alternative medicine: herbs, phytochemicals and vitamins and their immunologic effects[END_REF]. The global acceptance and public concern in the use of herbal medicines, phytonutrients or nutraceuticals continue to assume exponential increase. It has been estimated that up to 80% of people worldwide relying on them as a primary source of healthcare [START_REF] Ekor | The growing use of herbal medicines: issues relating to adverse reactions and challenges in monitoring safety[END_REF]. This concern in drugs of natural origin is related to numerous reasons, namely, the traditional medicine is more affordable, closer to the patient's ideology and receives greater public access than chemical synthesized treatment. Furthermore, abusive and/or incorrect use of conventional medicines results in some cases in harmful side effects [START_REF] Wachtel-Galor | Herbal medicine: An introduction to its history, usage, regulation, current trends, and research needs[END_REF]. The use of aromatic and medicinal plants is incessantly expanding due to increasing consumers demand and concern in these plants for several applications. In fact, consumers are becoming more and more aware of the benefits of inherent practice of medicinal and aromatic plants and their metabolites [START_REF] Chikezie | Bioactive principles from medicinal plants[END_REF][START_REF] Rates | Plants as source of drugs[END_REF]. These plants produce a large variety of secondary metabolites; among them, essential and vegetable oils deserve particular attention [START_REF] Dhifi | Essential oils' chemical characterization and investigation of some biological activities: A critical review[END_REF][START_REF] Kumar | Vegetable oil: Nutritional and industrial perspective[END_REF][START_REF] Pandey | Essential oils: Sources of antimicrobials and food preservatives[END_REF][START_REF] Yara-Varón | Vegetable oils as alternative solvents for green oleo-extraction, purification and formulation of food and natural products[END_REF].

Essential oils (EO) comprised volatile and semi-volatile organic compounds determining the specific aroma, flavor and fragrance of plants. They are volatile and instable at roomtemperature. In the other hand, vegetable oils (VO) consist of esters of glycerol and fatty acids and are nonvolatile and stable at room temperature [START_REF] Moghaddam | Chemistry of essential oils and factors influencing their constituents[END_REF][START_REF] Sagiri | A Review on encapsulation of vegetable oils : Strategies, preparation methods and application[END_REF]. Besides being edible in their refined or virgin form, VO play a crucial role in therapeutic and prophylactic prevention of diseases such as inflammation, diabetes, cancer and atherosclerosis [START_REF] Ganesan | Impact of consumption and cooking manners of vegetable oils on cardiovascular diseases-A critical review[END_REF][START_REF] Kochikuzhyil | Effect of saturated fatty acid-rich dietary vegetable oils on lipid profile, antioxidant enzymes and glucose tolerance in diabetic rats[END_REF][START_REF] Saha | Antioxidant effect of vegetable oils containing conjugated linolenic acid isomers against induced tissue lipid peroxidation and inflammation in rat model[END_REF][START_REF] Yu | Studies on the chemopreventive potentials of vegetable oils and unsaturated fatty acids against breast cancer carcinogenesis at initiation[END_REF]. Subsequently, EO received significant attention in food, agricultural and pharmaceutical fields due to their antioxidant, antibacterial, antiviral and antifungal properties.

The diverse health benefits associated with the consumption of EO constitute an area of intense research [START_REF] Ali | Essential oils used in aromatherapy: A systemic review[END_REF][START_REF] Dhifi | Essential oils' chemical characterization and investigation of some biological activities: A critical review[END_REF][START_REF] Elshafie | An overview of the biological effects of some mediterranean essential oils on human health[END_REF]. Meantime, the benefits linked to these bioactive agents is generally hampered by several obstacles. For instance, the oxidation is the main problem limiting the use of VO in several fields. The unsaturated fatty acids present in VO lead to increase the risk of lipid oxidation which in turn result in producing numerous free radical species, primary oxidation products such as lipid hydroperoxides and secondary oxidation products such as hydrocarbons, epoxides, ketones and aldehydes that negatively impact aroma. Moreover, VO oxidation can generate toxic products that can largely affect biological tissues [START_REF] Chen | Minor components in food oils : A critical review of their roles on lipid oxidation chemistry in bulk oils and emulsions[END_REF][START_REF] Matthäus | Oxidation of edible oils[END_REF]. At the same time, numerous studies have evidenced that EO are unstable and degraded easily if they are not protected from external factors like oxidation, volatilization, heat and light [START_REF] Turek | Stability of essential oils: A review[END_REF].

Besides all these, the low water solubility, low permeation and low bioavailability of plant oils in biological fluids and tissues constitute other factors that limit their rational use [START_REF] Dima | Bioavailability and bioaccessibility of food bioactive compounds; overview and assessment by in vitro methods[END_REF][START_REF] Rein | Bioavailability of bioactive food compounds: a challenging journey to bioefficacy[END_REF]. Therefore, designing suitable carriers by using nanoencapsulation approach is crucial to overcome restrictions outlined (El-Asbahani et al., 2015;[START_REF] Sagiri | A Review on encapsulation of vegetable oils : Strategies, preparation methods and application[END_REF]. [START_REF] Hoyos-Leyva | Characterization of spray drying microencapsulation of almond oil into taro starch spherical aggregates[END_REF] revealed that the encapsulation of almond oil in starch microcapsules conferred more protection against oxidation when compared to unencapsulated oil. Similar results were already reported when investigating the stability of linseed, jasmine and holy basil oils-loaded nanoparticles against heat, oxidation and volatilization as compared to the free oils [START_REF] Lv | Formation of heat-resistant nanocapsules of jasmine essential oil via gelatin / gum arabic based complex coacervation[END_REF][START_REF] Rubilar | Development of a soup powder enriched with microencapsulated linseed oil as a source of omega-3 fatty acids[END_REF][START_REF] Sutaphanit | Optimisation of microencapsulation of holy basil essential oil in gelatin by response surface methodology[END_REF].

Moreover, several studies have evidenced the amelioration of plant oils biological performance after being incorporated in nanosystems. [START_REF] Alaarg | Docosahexaenoic acid liposomes for targeting chronic inflammatory diseases and cancer : an in vitro assessment[END_REF] depicted that the encapsulation of docosahexaenoic acid in liposomes improve its anticancer activity. [START_REF] Zhaveh | Encapsulation of Cuminum cyminum essential oils in chitosancaffeic acid nanogel with enhanced antimicrobial activity against Aspergillus flavus[END_REF] related the superior performance of Cuminum cyminum EO nanogels against Aspergillus flavus as compared to the free oil to the increased surface area of the nanoparticles.

Depending on the preparation method, nanocarriers can be mainly classified into two main groups: polymer-based nanocarriers and lipid-based nanocarriers. Among the several colloidal systems investigated in drug delivery, polymeric nanoparticles (pNPs), liposomes and solid lipid nanoparticles (SLN) gained more interest [START_REF] Allen | Liposomal drug delivery systems: from concept to clinical applications[END_REF]El-say and Elsawy, 2017;[START_REF] Geszke-Moritz | Solid lipid nanoparticles as attractive drug vehicles: Composition, properties and therapeutic strategies[END_REF][START_REF] Immordino | Stealth liposomes: Review of the basic science, rationale, and clinical applications, existing and potential[END_REF][START_REF] Mehnert | Solid lipid nanoparticles: Production, characterization and applications[END_REF][START_REF] Rani | Polymeric nanoparticles in targeting and delivery of drugs[END_REF]. In this context, the present review covers literature data summarizing the current development of nanocarrier systems for plant oils delivery with a focus on the main properties and preparation technique of pNPs, liposomes and SLN. In addition, the chemical composition of both essential and vegetable oils along with the emerging and potential applications of plant oils loaded nanocarriers in several fields were explored.

Chemical composition of vegetable oils

Vegetable oils, also named non-essential or fixed oils, are fats usually extracted from plant seeds (e.g., soybean oil, rapeseed oil, sesame oil etc.), or less often from other parts of fruits (e.g., olive oil, palm oil etc.), by simple pressing and/or solvent extraction process [START_REF] Yara-Varón | Vegetable oils as alternative solvents for green oleo-extraction, purification and formulation of food and natural products[END_REF]. Depending on the origin, the crop, the season, and the producing methods, their composition is highly variable and complex [START_REF] Lligadas | Plant oils as platform chemicals for polyurethane synthesis : current state-of-the-art[END_REF].

Triglycerides

The main components of VO are triglycerides; they represent 95 to 98% of the global constituents depending on the source of oil [START_REF] Yara-Varón | Vegetable oils as alternative solvents for green oleo-extraction, purification and formulation of food and natural products[END_REF]. The word 'oil' hereby refers to triglycerides that are liquid at room temperature (Guner et al., 2006). Triglycerides are composed of three fatty acid molecules esterified to one glycerol molecule, as demonstrated in Fig. 1 [START_REF] Miao | Vegetable-oil-based polymers as future polymeric biomaterials[END_REF]. Depending on the saturation degree of fatty acids, triglycerides are classified into saturated, mono-and poly-unsaturated fatty acids. The characteristics of VO depend on several parameters including; i) fatty acid chain length, ii) the degree of unsaturation, and iii) the stereochemistry of the double bonds [START_REF] Meier | Plant oil renewable resources as green alternatives in polymer science[END_REF]. Additionally, varieties in climatic, agronomic and cultivation may engender difference in fatty acid composition of triglycerides [START_REF] Yara-Varón | Vegetable oils as alternative solvents for green oleo-extraction, purification and formulation of food and natural products[END_REF].

Minor Components

Apart of triglycerides, VO contain also a diversity of non-triglyceride minor compounds (less than 5%) which present crucial biological properties and nutritional values for nutraceutical and pharmaceutical industries (Fig. 2) [START_REF] Yara-Varón | Vegetable oils as alternative solvents for green oleo-extraction, purification and formulation of food and natural products[END_REF]. They comprised two types: glycerolipids including monoglycerides, diglycerides and phospholipids; and nonglycerolipids such as tocopherols/tocotrienols, sterols, free fatty acids, pigments, vitamins, phenolic compounds, proteins and water [START_REF] Xenakis | Colloidal structures in natural oils[END_REF].

Chemical composition of essential oils

Essential oils are oily aromatic liquids extracted from different plant organs as secondary metabolites like, leaves (eucalyptus, thym, salvia), zest (citrus), flowers (lavender, rose, jasmine), fruits (citrus), seeds (sesame), roots (ginger) and wood (sandal) (El-Asbahani et al., 2015). The EO are generally complex mixtures of individual aroma compounds. Even they are not strictly oils, they are poorly soluble in water [START_REF] Calo | Essential oils as antimicrobials in food systems -A review[END_REF]. In last decades, innovative methods have been emerged to extract EO from plant raw materials [START_REF] Boukroufa | Bio-refinery of orange peels waste: A new concept based on integrated green and solvent free extraction processes using ultrasound and microwave techniques to obtain essential oil, polyphenols and pectin[END_REF][START_REF] Gavahian | Extraction of essential oils from Mentha piperita using advanced techniques: Microwave versus ohmic assisted hydrodistillation[END_REF][START_REF] Sodeifian | Application of supercritical carbon dioxide to extract essential oil from Cleome coluteoides Boiss: Experimental, response surface and grey wolf optimization methodology[END_REF][START_REF] Zermane | Optimization of Algerian rosemary essential oil extraction yield by supercritical CO2 using response surface methodology[END_REF]. The constituents of plant EO comprise mainly four main groups: terpenes, phenylpropanoids, straight-chain compounds and miscellaneous groups.

Terpenes

Terpenes are the most abundant compounds found in plant EO [START_REF] Chizzola | Regular monoterpenes and sesquiterpenes (essential oils)[END_REF]. They are synthesized via the mevalonic acid pathway in the cytoplasm of plant cells [START_REF] Morsy | Chemical structure, quality indices and bioactivity of essential oil constituents[END_REF].

Terpene compounds can be divided into two main categories: terpene hydrocarbons and oxygenated compounds [START_REF] Moghaddam | Chemistry of essential oils and factors influencing their constituents[END_REF].

Terpenes hydrocarbon

The essential building block of terpenes is the isoprene unit joined in a head-to-tail manner. Basing on the number of isoprene units, different terpenes can be found in EO, as demonstrated in Fig. 3 (El-Asbahani et al., 2015;[START_REF] Morsy | Chemical structure, quality indices and bioactivity of essential oil constituents[END_REF]. Terpenes hydrocarbons are the first main group of components composed completely of carbon and hydrogen atoms and varied significantly in size and complexity [START_REF] Moghaddam | Chemistry of essential oils and factors influencing their constituents[END_REF]. Monoterpenes and sesquiterpenes are the dominant terpenes found in plant EO. They are built up by two and three isoprene units, respectively. These terpenes could present acyclic, cyclic or aromatic structures.

Cyclic terpenes can be classified depending on their ring size into monocyclic, bicyclic or tricyclic terpenes (Table 1). These compounds oxidize rapidly due to their fast reaction to heat and air sources [START_REF] George | Isoprenoid drugs , biofuels , and chemicals -Artemisinin , Farnesene and Beyond[END_REF]. Diterpenes result by the combination of four isoprene units in a head-to-tail manner; they are essential constituents of plant resins [START_REF] Langenheim | Plant resins: chemistry, evolution, ecology and ethnobotany[END_REF]. Commonly, diterpenes, triterpenes and tetraterpenes are present in EOs at a very low concentration. Their content may vary with the extraction method [START_REF] Morsy | Chemical structure, quality indices and bioactivity of essential oil constituents[END_REF].

Terpenoids

Terpene can be changed by adding functional groups and become terpenoid. When a monoterpene or a sesquiterpene has a functional group added to it, it is known as a monoterpenoid or sesquiterpenoid; respectively. The suffix "oid" means "derived from" or "like" therefore "terpenoid" can refer to all molecules with a terpene-like structure [START_REF] Moghaddam | Chemistry of essential oils and factors influencing their constituents[END_REF]. They are classified into carboxylic acids, alcohols, aldehydes, esters, ethers, ketones, phenols, lactones, oxides, etc.

Phenylpropanoid

This class of compounds, derived from phenylpropene, is synthesized from the amino acid phenylalanine and l-tyrosine via the shikimic acid pathway. Their name is derived from the aromatic phenyl group and the propene tail. The propyl side chain may contain hydroxyl or carboxyl group; while the aromatic ring may carry methoxy, hydroxyl and methylene dioxy groups [START_REF] Morsy | Chemical structure, quality indices and bioactivity of essential oil constituents[END_REF]. Phenylpropanoids give a specific flavor and odor to the plant when they are present [START_REF] Moghaddam | Chemistry of essential oils and factors influencing their constituents[END_REF]. Eugenol and cinnamaldehyde are example of this group of constituents (Fig. 4).

Straight-chain compounds

This group contains only straight-chain compounds, not containing any side branches.

They range from n-heptane, to compounds with 35 carbon atoms. The leaf alcohol (3(Z)-hexen-1-ol) (Fig. 4) represents an example of this class; it gives an intense grassy-green odor upon cutting green grass and leaves [START_REF] Morsy | Chemical structure, quality indices and bioactivity of essential oil constituents[END_REF].

Miscellaneous group

They issue from the degradation of unsaturated fatty acids, lactones, terpenes, glycosides and represent sulfur-and nitrogen-containing compounds. Diallyl disulfide and indole are example of this class of compounds (Fig. 4) [START_REF] Morsy | Chemical structure, quality indices and bioactivity of essential oil constituents[END_REF].

Limitation in clinical use of plant oils

Since ancient times, EO have been recommended all over the world for a variety of health problems and diseases [START_REF] Moghaddam | Chemistry of essential oils and factors influencing their constituents[END_REF]. Enormous studies have investigated the biological properties of EO, including antimicrobial, antifungal [START_REF] Ceole | Nerolidol, the main constituent of Piper aduncum essential oil, has anti-Leishmania braziliensis activity[END_REF][START_REF] Garcia-Rellán | Chemical composition, herbicidal and antifungal activity of Satureja cuneifolia essential oils from Spain[END_REF], antiviral [START_REF] Zeghib | Antibacterial, antiviral, Antioxidant and antiproliferative activities of Thymus guyonii essential oil[END_REF], insecticidal [START_REF] Chen | Trans-cinnamaldehyde, an essential oil in cinnamon powder, ameliorates cerebral ischemia-induced brain injury via inhibition of neuroinflammation through attenuation of iNOS, COX-2 expression and NFκ-B signaling pathway[END_REF][START_REF] Jassbi | Chemical composition and biological activity of the essential oil and solvent extracts of Scaligeria nodosa[END_REF], antioxidant [START_REF] Hassanen | Antioxidant and antimicrobial activity of celery (Apium graveolens) and coriander (Coriandrum sativum) herb and seed essential oils[END_REF][START_REF] Limaverde | Inhibition of the TetK efflux-pump by the essential oil of Chenopodium ambrosioides L. and α-terpinene against Staphylococcus aureus IS-58[END_REF], anticancer [START_REF] Carneiro | Chemical composition, antioxidant and antibacterial activities of essential oils from leaves and flowers of Eugenia klotzschiana Berg (Myrtaceae)[END_REF][START_REF] Thakre | Effects of cinnamaldehyde , ocimene , camphene , curcumin and farnesene on Candida albicans[END_REF], antidiabetic [START_REF] Tahir | Chemical composition and antidiabetic activity of essential oils obtained from two spices (Syzygium aromaticum and Cuminum cyminum)[END_REF], anti-inflammatory [START_REF] Chansang | Potential of natural essential oils and cinnamaldehyde as insecticides against the dengue vector Aedes Aegypti (Diptera: Culicidae). Southeast Asian J[END_REF][START_REF] Nonato | Anti-inflammatory properties of rose oxide[END_REF], antihypertensive [START_REF] Cherkaoui-Tangi | Vasorelaxant effect of essential oil isolated from Nigella sativa L. seeds in rat aorta: Proposed mechanism[END_REF] and immunomodulatory [START_REF] Orhan | Immunomodulatory properties of various natural compounds and essential oils through modulation of human cellular immune response[END_REF][START_REF] Ozek | Chemical composition and phagocyteimmunomodulatory activity of Ferula iliensis essential oils[END_REF]. In medical field, EO have been used against nosocomial infections, as a cleaning liquid for disinfection of medical equipment and surfaces [START_REF] Warnke | The battle against multi-resistant strains: Renaissance of antimicrobial essential oils as a promising force to fight hospital-acquired infections[END_REF] or as an aerosol in operating blocks and waiting rooms for air cleaning to limit contaminations [START_REF] De Billerbeck | Huiles essentielles et bactéries résistantes aux antibiotiques[END_REF]. The application of EO has emerged to food and agriculture fields. They are used as antioxidants and preservatives in food [START_REF] Khosravi | Essential oils as natural food preservatives: Antimicrobial and antioxidant applications[END_REF][START_REF] Pandey | Essential oils: Sources of antimicrobials and food preservatives[END_REF], as plant and crop protectants [START_REF] Abdullah | Plant essential oils as grain protectants against Rhizopertha dominica (Coleoptera:Bostrichidae) during storage[END_REF] and incorporated into foodstuff packaging [START_REF] Ribeiro-Santos | Use of essential oils in active food packaging: Recent advances and future trends[END_REF].

In the other side, VO is a source of everlasting components which are responsible of pertinent biological properties. Many of the fatty acids and other compounds present in VO have long been known to benefit our health. Numerous experimental studies approved that a dietary intake of omega-3 polyunsaturated fatty acids can reduce inflammation and may prevent the risk of chronic diseases like heart disease, cancer, and arthritis [START_REF] Gammone | Omega-3 polyunsaturated fatty scids: Benefits and endpoints in Sport[END_REF][START_REF] Hardman | Polyunsaturated fatty acids as dietary supplements: Biological activities and sources[END_REF][START_REF] Kris-Etherton | Omega-3 fatty acids and cardiovascular disease: New recommendations from the american heart association[END_REF]. In addition, polyphenols, medium chain fatty acids and tocopherol present in some VO were the reason of their antioxidant and antistress activities [START_REF] Duthie | The Contribution of d αtocopherol and d γ -tocopherol to the antioxidant capacity of several edible plant oil[END_REF][START_REF] Yaep | Antistress and antioxidant effects of virgin coconut oil in vivo[END_REF]. Current animal studies have indicated that palmitic acid had a potent antiviral property against HIV-1 and HIV-2 (Özçelik et al., 2005).

Linoleic and oleic acids were considered as effective antibacterial agents [START_REF] Dilika | Antibacterial activity of linoleic and oleic acids isolated from Helichrysum pedunculatum: a plant used during circumcision rites[END_REF].

Further experimental studies highlighted other biological benefits of VO such as antiinflammatory [START_REF] Hsu | Anti-inflammatory and antioxidant effects of sesame oil on atherosclerosis: A descriptive literature review[END_REF], analgesic and antipyretic [START_REF] Intahphuak | Anti-inflammatory, analgesic, and antipyretic activities of virgin coconut oil[END_REF], hypolipidemic [START_REF] Ali | Hypolipidemic and hypocholesterolemic effect of roselle (Hibiscus sabdariffa L.) seeds oil in experimental male rats[END_REF], antibacterial [START_REF] Tabassum | In vitro antimicrobial activity of edible oils against human pathogens causing skin infections[END_REF], antiviral [START_REF] Orhan | Evaluation of antibacterial, antifungal, antiviral, and antioxidant potentials of some edible oils and their fatty acid profiles[END_REF], hepatoprotective and gastroprotective properties [START_REF] Cheng | Beneficial effects of camellia oil (Camellia oleifera Abel.) on hepatoprotective and gastroprotective activities[END_REF].

In the pharmaceutical field, plant oils entered in the composition of many dosage forms through several pathways, including the cutaneous route (creams, ointments, massage oils, gels), the oral route (tablets, syrup, capsules), the rectal route (suppositories) and the pulmonary route (aerosols, nasal drops, sprays) (El-Asbahani et al., 2015). Despite that, the preparations based on plant oil have some important constraints. The VO oral delivery is always confronted to their low solubility in biological fluids, low permeation and poor bioavailability because of their possible oxidation in the gastrointestinal tract [START_REF] Márquez-Ruiz | Changes and effects of dietary oxidized lipids in the gastrointestinal tract[END_REF]. For instance, [START_REF] Kanner | The stomach as a bioreactor: dietary lipid peroxidation in the gastric fluid and the effects of plant-derived antioxidants[END_REF] suggested that the adsorbed oxygen and low pH of the human gastric fluid may enhance the oxidation of VO in the presence of catalysts found in foods.

Moreover, it was reported that hydroperoxide resulted from the hydrolysis of triacylglycerol contained in VO by pancreatic lipase are not likely to be absorbed in their intact form [START_REF] Suomela | Diet and lipoprotein oxidation: Analysis of oxidized triacylglycerols in pig lipoproteins[END_REF].

Additionally, the toxicity and irritation effects of EO on the oesophageal and gastro intestinal mucosa limit also their uses. EO could be the reason of potential allergic reactions of the skin if they are undiluted or insufficiently diluted [START_REF] Pedro | The use of nanotechnology as an approach for essential oil-based formulations with antimicrobial activity[END_REF][START_REF] Warshaw | North American contact dermatitis group patch test results: 2011-2012[END_REF].

For instance, applying excessive amounts of cinnamaldehyde rich-EO to a large surface of the skin can result in significant allergic reaction and anaphylactic shock, which in turn may be fatal [START_REF] Diba | Contact urticaria from cinnamal leading to anaphylaxis[END_REF]. Some oils like those extracted from cumin, bergamot, verbena and lemon can cause photosensitization and induce malignant skin changes like redness, itching, burns, hyperpigmentation, pigmentary changes or berloque dermatitis [START_REF] Zammit | Photosensitivity : Light , sun and pharmacy[END_REF].

Moreover, the high volatility and the high risk of deterioration of EO upon their direct exposure to heat, humidity, light, or oxygen discourages their free use, i.e. without a pharmaceutical vehicle [START_REF] Turek | Stability of essential oils: A review[END_REF]. Therefore, the nanoncapsulation has been considered as a key to overcome the mentioned limitations (El-Asbahani et al., 2015;[START_REF] Sagiri | A Review on encapsulation of vegetable oils : Strategies, preparation methods and application[END_REF].

Encapsulation strategies help in converting oils into several dosage forms including, liquid, solid or semi-solid dosage forms and thus enables retention of their activity for longer periods of time [START_REF] Sagiri | A Review on encapsulation of vegetable oils : Strategies, preparation methods and application[END_REF]. Nanocarriers protect plant oils from environmental factors such as pH, oxygen, light etc., serving as barrier between the molecule and the environment.

They also shield the oils from oxidative degradation, evaporation and photo-degradation [START_REF] Bilia | Essential oils loaded in nanosystems : A developing strategy for a successful therapeutic approach. Evidence-Based Complement[END_REF]. Their ability to control oil release confers improved efficacy, reduced toxicity, improved patient compliance and convenience (El-Asbahani et al., 2015;[START_REF] Zhao | Solid lipid nanoparticles for sustained pulmonary delivery of Yuxingcao essential oil: Preparation, characterization and in vivo evaluation[END_REF].

Plant oils-loaded nanodelivery systems

Nanodelivery systems is an area of intense research as they provide a number of benefits for therapy, such as (i) high drug efficacy, specificity and tolerability, (ii) sustained and controlled release of drugs (iii) less risk of toxicity (iv) deep tissue diffusion due to the nanometric size, and (iv) protection of drugs at both extracellular and intracellular levels [START_REF] Bilia | Essential oils loaded in nanosystems : A developing strategy for a successful therapeutic approach. Evidence-Based Complement[END_REF][START_REF] Kumari | Biodegradable polymeric nanoparticles based drug delivery systems[END_REF]. In this paper, we highlighted the different experimental strategies designed to encapsulate plants oils into two main groups of organic nanocarriers; polymer based-nanocarriers (including polymeric nanoparticles) and lipid based-nanocarriers (including liposomes and solid lipid nanoparticles).

Encapsulation in polymer-based nanocarriers

Polymeric nanoparticles (pNP) are submicronic core-shell spherical systems prepared from natural or synthetic polymers [START_REF] Mattheolabakis | Nanodelivery strategies in cancer chemotherapy: biological rationale and pharmaceutical perspectives[END_REF]. Depending on the nanoparticle preparation process, nanocapsule or nanosphere can be obtained. Nanospheres have a matrixlike form in which the drug is evenly distributed. Nanocapsules are, however, vesicular structures in which the drug is confined in an inner core surrounded by a polymeric membrane [START_REF] Crucho | Polymeric nanoparticles: A study on the preparation variables and characterization methods[END_REF]) (Fig. 5). Many polymers were used for this purpose, notably, biodegradable polyesters like poly(lactide-co-glycolide), polylactide and poly (ε-caprolactone) were widely used [START_REF] Froiio | Chapter 16 -Polymer-based nanocontainers for drug delivery[END_REF]. Recently, pNP are extensively studied for plant oil delivery in view of their ability to entrap and protect oils, biodegradability, bioavailability and their high stability. The plant oil may be conjugated with the polymer (matrix or wall) or entrapped in the oily core [START_REF] Bilia | Essential oils loaded in nanosystems : A developing strategy for a successful therapeutic approach. Evidence-Based Complement[END_REF]. Several methods have been reported for developing pNP while the nanoprecipitation, the ionic gelation, the emulsification/solvent evaporation and spray drying methods, are extensively used and Fig. 5 demonstrates the principle of each technique.

Spray drying

Spray-drying technique has been used for decades to encapsulate plant oils in microand nano polymeric particles. It is based on the conversion of an infeed (solution, emulsion or suspension) into a dry powder in a single and continuous step. With respect to the encapsulation of plant oil, oil in water emulsion was atomized into fine drops in a drying chamber where hot air is passed (150-250°C). A fast evaporation of water occurred leading to the instantaneous formation of powder (Fig. 5.d) [START_REF] Encina | Conventional spray-drying and future trends for the microencapsulation of fish oil[END_REF][START_REF] Matos | Essential oils in nanostructured systems : Challenges in preparation and analytical methods[END_REF]. Spray drying technique is extensively used to encapsulate both essential and vegetable oils in micro and nanoparticles, as illustrated in Table 1.

Regarding the particle size and the encapsulation efficiency (EE%) of the particles produced by spray drying technique, high average diameter with moderate oil entrapment amount have been reported by numerous work studies, as depicted in Table 1. [START_REF] Hoyos-Leyva | Characterization of spray drying microencapsulation of almond oil into taro starch spherical aggregates[END_REF] reported that almond oil loaded taro starch particles had an average size ranging from 1.4 to 31.1µm with an EE% of 37.5%. In addition, [START_REF] De-Oliveira | Alginate / cashew gum nanoparticles for essential oil encapsulation[END_REF] found that Lippia sidoides EO loaded alginate : cashew gum nanoparticles exhibited a spherical shape with size ranging from 223 to 399 nm, zeta potential values in range of -30 to -36 mV and EE% of about 50 %. In another work, the same EO was encapsulated in chitosan : cashew gum based nanoparticles owning an EE% of 70% with an average particle sizes in the range 335-558 nm [START_REF] Abreu | Chitosan/cashew gum nanogels for essential oil encapsulation[END_REF]. Furthermore, the mixture maltodextrin : soy protein was used to encapsulate walnut oil and the resultant particles showed an average diameter of 4 to 10 µm with an EE% equal to 60% [START_REF] González | Study of the preparation process and variation of wall components in chia (Salvia hispanica L.) oil microencapsulation[END_REF].

The main feature of spray drying method is the formation of special particles. Indeed, the scanning electron microscopy carried by [START_REF] Tonon | Influence of emulsion composition and inlet air temperature on the microencapsulation of flaxseed oil by spray drying[END_REF] on flaxseed oil loaded microparticles revealed the formation of hollow particles, i.e. particles with concave and shriveled surfaces. Same images were found by Gallardo et al. when visualizing linseed oilloaded gum arabic microcapsules. They ascribed this form to vacuoles formation inside the particles after the crust development. The magnitude of this process is inversely related to solid concentration in the emulsion [START_REF] Gallardo | Microencapsulation of linseed oil by spray drying for functional food application[END_REF]. Moreover, [START_REF] Wang | Development and evaluation of microencapsulated peony seed oil prepared by spray drying : Oxidative stability and its release behavior during invitro digestion[END_REF] carrying out confocal scanning laser microscopy on peony seed oil microparticles stated that the spray dried particles had a complete core-shell structure with smooth surface and no apparent fissures or cracks.

In vitro release profile of plant oils from particles prepared by spray drying technique generally exhibit a controlled manner. In a study carried out by [START_REF] De-Oliveira | Alginate / cashew gum nanoparticles for essential oil encapsulation[END_REF] the nanoparticles have reached a level of maximal release around 30-50 h. In that time, the content of Lippia sidoides EO from alginate : cashew gum particles varied from 45 and 95% depending on the ratio of used polymers. Higher and faster release rate was achieved with high amount of cashew gum due to its greater hydrophilic character which allows greater diffusion of EO through the polymeric wall. Conversely, a smaller and more controlled release was assessed when increasing alginate content; after 50h, only 45% of oil was released. This was related to the formation of compact network which in turn slow down the diffusion of EO to the external medium [START_REF] De-Oliveira | Alginate / cashew gum nanoparticles for essential oil encapsulation[END_REF].

Particles produced by spray drying process provides a high stability for encapsulated oils. In this context, Hoyos-leyva et al. ( 2019) investigated the oxidative stability of almond oil before and after encapsulation into taro starch microcapsules. They found that these systems conferred more protection against oxidation when compared to unencapsulated almond oil due to the relatively reduced porosity of the material, which in turn limits the exposure of the oil to stress conditions during storage.

Several parameters have to be taken into consideration to efficiently entrap plant oils in polymeric micro-and nanoparticles by spray drying technique. The influence of type and amount of wall material on plant oils-loaded particles characteristics has been extensively studied in the literature [START_REF] Bae | Microencapsulation of avocado oil by spray drying using whey protein and maltodextrin[END_REF][START_REF] Chin | Microencapsulation of refined kenaf (Hibiscus cannabinus L.) seed oil by spray drying using β -cyclodextrin / gum arabic / sodium caseinate[END_REF][START_REF] Gallardo | Microencapsulation of linseed oil by spray drying for functional food application[END_REF][START_REF] Laohasongkram | Microencapsulation of macadamia oil by spray drying[END_REF][START_REF] Lozano | Microencapsulation of extra-virgin olive oil by spray-drying : Influence of wall material and olive quality[END_REF][START_REF] Rodea-González | Spray-dried encapsulation of chia essential oil (Salvia hispanica L.) in whey protein concentrate-polysaccharide matrices[END_REF][START_REF] Rubilar | Development of a soup powder enriched with microencapsulated linseed oil as a source of omega-3 fatty acids[END_REF][START_REF] Shamaei | Microencapsulation of walnut oil by spray drying : Effects of wall material and drying conditions on physicochemical properties of microcapsules[END_REF]. [START_REF] Carneiro | Encapsulation efficiency and oxidative stability of flaxseed oil microencapsulated by spray drying using different combinations of wall materials[END_REF] investigated the microencapsulation of flaxseed oil by spray drying technique. They studied the potential of maltodextrin mixed with different wall materials: arabic gum, whey protein concentrate and two types of modified starch (Hi-Cap 100TM and Capsul TA) on droplets size. Results showed that the highest viscosity presented by maltodextrin : arabic gum emulsion implies a higher resistance to droplets movement, thus preventing coalescence and leading to smaller droplets size. [START_REF] Shamaei | Microencapsulation of walnut oil by spray drying : Effects of wall material and drying conditions on physicochemical properties of microcapsules[END_REF] related the differences in the mean droplet size of the emulsions using different wall material to the surface activity and molecular weight of wall material constituents. They found that as the ratio of tween 80 to skim milk powder increases, the mean droplet size decreases. This in turn was attributed to the fact that tween 80 mitigated droplet coalescence and Ostwald ripening phenomena in the emulsion by reducing the surface tension and interfacial free energy of the emulsion. In another study, emulsion droplet size was found to decrease as the ratio of wall to core material increases due to the fact that at low ratio, there may not be enough coating materials to cover the whole surface of the droplets in order to prevent them from coalescence which in turn increases the droplet size [START_REF] Rodea-González | Spray-dried encapsulation of chia essential oil (Salvia hispanica L.) in whey protein concentrate-polysaccharide matrices[END_REF]. Same result was also reported for chia seed oil-loaded microcapsules prepared by spray drying process [START_REF] Laohasongkram | Microencapsulation of macadamia oil by spray drying[END_REF]. Moreover, [START_REF] Chew | Microencapsulation of refined kenaf (Hibiscus cannabinus L.) seed oil by spray drying using β -cyclodextrin / gum arabic / sodium caseinate[END_REF] spotlighted that adding βcyclodextrin to the wall matrix increases the EE% of refined kenaf seed oil due to its host-guest character. In fact, its interior cavity acts as a host which can fix the guest (hydrophobic oil), while the exterior surface can bind with water or hydrophilic head of other wall materials. Furthermore, Us-medina and coworkers (2018) stated that adding chia mucilage to sodium caseinate : maltodextrin wall matrix increases the EE% of chia seed oil from 71.26 to 86.65%.

They attributed this result to the fact that chia mucilage, used as thickener agent, increases the viscosity of the system which in turn promotes a greater physical stability of the emulsion during the spray drying process.

With respect to the oil content, [START_REF] Rubilar | Development of a soup powder enriched with microencapsulated linseed oil as a source of omega-3 fatty acids[END_REF] revealed that increasing the oil concentration provokes a significant increase in droplet emulsion size and viscosity, which in turn reduces the EE% and increases the surface oil content of the powder leading to potential lipid oxidation. Similar result was already published [START_REF] Tonon | Microencapsulation of flaxseed oil by spray drying : Effect of oil load and type of wall material[END_REF].

Air inlet temperature is another factor to take into account for the development of plant oil-loaded particles; and it was widely investigated in the literature (Frascareli et al., 2011;[START_REF] Laohasongkram | Microencapsulation of macadamia oil by spray drying[END_REF][START_REF] Roccia | Influence of spray-drying operating conditions on sunflower oil powder qualities[END_REF][START_REF] Shamaei | Microencapsulation of walnut oil by spray drying : Effects of wall material and drying conditions on physicochemical properties of microcapsules[END_REF]). Frascareli et al. ( 2011) studied the encapsulation of coffee oil and observed that as the air flow temperature increases the EE% decreases due to the fact that higher temperature leads to faster drying of the external phase which creates cracks in the particle wall, resulting in oil loss. Moisture content is an important variable for the shelf life of powders. It was reported that increasing the inlet temperature reduced the moisture content [START_REF] Mohammed | Process conditions of spray drying microencapsulation of Nigella sativa oil[END_REF]. However, higher values (more than 175 °C) resulted in an increase in moisture content due to the formation of rapid crust which hampered the water evaporation leading to particles with more moisture content.

The particle size is another parameter which vary when modifying the air inlet temperature. In 2017, Mohammed and coworkers pointed out that an increased inlet air temperature produced larger-sized Nigella sativa EO particles and ascribed this result to the microcapsule structure. Indeed, high temperature enable the particles to form early which in turn prevents the shrinkage of particles during drying [START_REF] Mohammed | Process conditions of spray drying microencapsulation of Nigella sativa oil[END_REF].

To sum up, despite of the high temperature required, the spray drying method is widely used to encapsulate either essential or vegetable oils. This was related to the fact that short time of contact between hot air and plant oil occurred, and thus the evaporation happens between 15 and 30 seconds and takes place at the surface of the particle; hence , the oils never reach the inlet temperature of drying gas (Fang and Bhandari, 2012). According to Table 1, natural polymers like maltodextrin, gums and chitosan are the mostly used wall materials. Currently, this technique is widely used in nutraceutical and food industry due to its benefits including i) ease of scaling up, ii) simplicity, iii) low production costs, and iv) ability to produce microparticles facile to the transport and storage. Many drawbacks are associated to the use of this process including the lack of uniformity; high particle size, low oil loading and possibility of oil loss. Moreover, the wall material used must have good water solubility as most formulations used by the food industry are aqueous-based and simultaneously impart a suitable viscosity in order to enable the drying process [START_REF] Corrêa-Filho | Advances in the application of microcapsules as carriers of functional compounds for food products[END_REF].

Emulsion evaporation

Emulsion evaporation method has been proposed by [START_REF] Vanderhoff | Polymer emulsification process[END_REF] to develop pNPs. In this process, an organic solution consisting of polymer and oil is emulsified with a non-solvent mixture under a high shear stress (e.g. by high-shear homogenization or ultrasonication). After that, the organic solvent is evaporated either by continuous magnetic stirring at room temperature or under reduced pressure leading to nanoparticles formation (Fig. 5.b) [START_REF] Rao | Polymer nanoparticles : Preparation techniques and sizecontrol parameters[END_REF][START_REF] Rodríguez | Current encapsulation strategies for bioactive oils : From alimentary to pharmaceutical perspectives[END_REF]. This technique has been used to encapsulate both essential and vegetable oils in pNPs, as depicted in Table 1.

The emulsion evaporation technique produces nanoparticles with higher EE% and smaller average diameter, as compared to the spray drying technique. In this context, Gomes et al. (2011a) reported a particle size of 179.3 and 173.8 nm with an EE% of 98 and 92% for eugenol-and trans-cinnamaldehyde loaded poly (lactide-co-glycolide) nanoparticles, respectively. Similarly, chia seed oil loaded nanoparticles using chia mucilage as wall material exhibited a small particle size (205 nm) with negative zeta potential (-11.58 mv) and high EE% (82.8%) [START_REF] Campo | Nanoencapsulation of chia seed oil with chia mucilage (Salvia hispanica L.) as wall material: characterization and stability evaluation[END_REF]. Moreover, poly (lactide-co-glycolide) nanoparticles were prepared to encapsulate clove EO, rich in eugenol which has potent antimicrobial activities [START_REF] Priyadarshini | Formulation and characterisation of poly ( lactic-co-glycolic acid ) encapsulated clove oil nanoparticles for dental applications[END_REF]. The average size of the resultant nanoparticles was about 237 nm with negative zeta potential of -40 mv and an EE% equal to 93%.

The nanoparticles prepared by emulsion evaporation process exhibited in vitro release pattern similar to that of particles produced by spray drying. In 2018, Priyadarshini et al. pointed out that in vitro cumulative clove EO release form poly (lactide-co-glycolide) nanoparticles followed a biphasic profile with an initial burst release at the first 4h due to the release of clove EO found near the nanoparticles surface [START_REF] Priyadarshini | Formulation and characterisation of poly ( lactic-co-glycolic acid ) encapsulated clove oil nanoparticles for dental applications[END_REF]. A cumulative amount of 75% was progressively released up to ∼15 days. Similar in vitro release kinetics were governed by eugenol and trans-cinnamaldehyde from poly (lactide-co-glycolide) nanoparticles where 64 and 87% of the initial load was released in the medium within 72 h, respectively (Gomes et al., 2011a).

The stability of the pNPs formulated by this technique was investigated in the literature.

In 2017, Campo et al. studied the oxidation of chia seed oil by gas chromatography with flame ionization detector in both emulsions and chia seed mucilage based-nanoparticles at accelerated conditions (40±1°C) during 28 days of storage [START_REF] Campo | Nanoencapsulation of chia seed oil with chia mucilage (Salvia hispanica L.) as wall material: characterization and stability evaluation[END_REF]. No significant change was shown in term of particle size, zeta potential or polydispersity index. However, the fatty acid methyl esters content reduction in pNPs was smaller than in emulsions; therefore, the chia seed mucilage provided a high protection against oil oxidation [START_REF] Campo | Nanoencapsulation of chia seed oil with chia mucilage (Salvia hispanica L.) as wall material: characterization and stability evaluation[END_REF].

With respect to the emulsification evaporation process, several parameters may affect the nanoparticles properties. [START_REF] Freiberger | Encapsulation of roasted coffee oil in biocompatible nanoparticles[END_REF] investigated the effect of polymer type (poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/polylactide); dispersion mechanism (ultrasonication / high shear homogenization) and polymer : oil ratio on the average size and oil recovery of biocompatible nanoparticles containing coffee oil. The statistical analysis showed non-significant effect of the experimental factors on the nanoparticle size within the experimental range. While for the coffee oil recovery, regression analysis produced a significant model. Less oil was lost by volatilization when sonication was used, because the required dispersion time (3min) was smaller when compared to the ultraturrax time (10min). Results

showed also that less coffee oil loss was pronounced when using poly(3-hydroxybutyrate-co-3-hydroxyvalerate) combined to the high shear homogenization as well as using polylactide combined with sonication. This was explained by the high viscosity of poly(3hydroxybutyrate-co-3-hydroxyvalerate)-dichloromethane solution which could avoid oil volatilization even with high shear homogenization [START_REF] Freiberger | Encapsulation of roasted coffee oil in biocompatible nanoparticles[END_REF]. Regarding the polymer:oil ratio, an increase in polymer amount lead to increase the viscosity of the solution resulting in efficient oil protection from the heat generated by the homogenizer.

To sum up, the emulsification evaporation method can be used to encapsulate both essential and vegetable oils. Although it provides high EE%, this method is less used to encapsulate plant oils, as compared to the spray drying technique. The possible reason behind this is the possible coalescence of droplets during evaporation which may lead to polydisperse particles and the need for a high shear process.

Nanoprecipitation

Nanoprecipitation is a simple, fast and increasingly trending technique for nanoparticles preparation [START_REF] Almoustafa | Technical aspects of preparing PEG-PLGA nanoparticles as carrier for chemotherapeutic agents by nanoprecipitation method[END_REF]. It was firstly reported by Fessi et al. (1989) and it is based on the interfacial deposition of polymers as a result of the displacement of a water miscible solvent from a lipophilic solution (Fig. 5.a) [START_REF] Miladi | Nanoprecipitation process : From particle preparation to in vivo applications[END_REF]. This method has been widely used to encapsulate plants oils in pNPs and Table 1 summarizes some work studies using the nanoprecipitation process to encapsulate either essential or vegetable oils during the last decade. [START_REF] Khoobdel | Insecticidal activity of polycaprolactone nanocapsules loaded with Rosmarinus officinalis essential oil in Tribolium castaneum (Herbst)[END_REF]. Furthermore, Babassu tree nut oil loaded-poly (lactideco-glycolide) nanoparticles exhibited an average diameter about 209.2 nm with a negative zeta potential of -15.8 mV [START_REF] Sousa | Nanostructured systems containing babassu (Orbignya speciosa) oil as a potential alternative therapy for benign prostatic hyperplasia[END_REF].

According to

In term of particle size, Esfandyari-Manesh and coworkers (2013) compared the nanoprecipitation to the emulsification solvent evaporation method to design carvone/anethole loaded poly (lactide-co-glycolide) nanoparticles and found that the particles produced by nanoprecipitation had smaller average diameter (158 and 126 nm for anethole and carvone, respectively) and narrower size distribution (0.08). Additionally, the amount of carvone and anethole were determined respectively by HPLC and UV analysis and results showed higher oil loading for the particles produced by nanoprecipitation (14.73 and 12.32% for anethole and carvone, respectively). The authors related the low EO loading for the emulsification method to its loss during the evaporation step which has taken a long time (about 3h). In addition, the high particle diameter of the nanoparticles prepared by this method was attributed to the difficulty for the mutual dispersion of the phase which is viscous due to the presence of high amount of oil and polymer.

According to the literature, to develop pNPs with suitable physicochemical properties, numerous factors had to be taken into consideration. The polymer type and amount have a critical effect on nanoparticles average size. In 2017, [START_REF] Khoobdel | Insecticidal activity of polycaprolactone nanocapsules loaded with Rosmarinus officinalis essential oil in Tribolium castaneum (Herbst)[END_REF] developing poly (ε-caprolactone) -based nanoparticles loaded with rosemary EO reported that increasing polymer quantity, leads in increasing the thickness of the particles shell and thus increasing their mean diameter, instead of increasing their number. Moreover, low values of EE% were observed when using Eudragit L100 as polymer for the encapsulation of Siberian cedar seed oil or free fatty acids due to its porous structure which enabled oil leakage [START_REF] Averina | Encapsulation of alimentary bioactive oils of the Baikal Lake area into pH-sensitive micro-and nanoparticles[END_REF]. Regarding the type of the EO, [START_REF] Liakos | Cellulose acetate -essential oil nanocapsules with antimicrobial activity for biomedical applications[END_REF] studied the influence of EO chemical composition on the particle size of three types of pNPs: Peppermint, cinnamon and lemongrass EOs loaded-cellulose acetate nanocapsules. The average size was increasing as follow: Cinnamon-pNPs ˂Peppermint-pNPs ˂Lemongrass pNPs. The larger pNPs were those containing lemongrass EO, due to the presence of high percentage of geranial and neral which have long carbon chains (≈10 C atoms) leading to larger pNPs when attached to cellulose acetate. While, peppermint contains mainly 35% menthol and 27% menthone leading to the creation of less uniform, complex and large nanoparticles. In the other hand, cinnamon EO consists essentially of cinnamaldehyde which reacts with hydroxyl group of cellulose acetate giving hemiacetal bound and hence combats the nanocapsules. Liakos and his coworkers assessed also in their study higher zeta-potential upon increasing lemongrass EO concentration, suggesting that some EO molecules are present onto the outer surface of the particles [START_REF] Liakos | Cellulose acetate -essential oil nanocapsules with antimicrobial activity for biomedical applications[END_REF]. Similarly, it was reported that the presence of lime EO decreased the zeta potential and the values were 61.1 and 57.0 mV for free-and loaded-chitosan nanocapsules, respectively.

They attributed this result to the diminution of free NH3 + groups of chitosan following their interaction with lime EO (Sotelo-Boyás et al., 2017b). However, in another work study, the presence of rosemary EO did not affect the zeta potential of poly (ε-caprolactone) nanoparticles which confirm its presence in the core of the nanoparticles instead of being adsorbed on their surface [START_REF] Khoobdel | Insecticidal activity of polycaprolactone nanocapsules loaded with Rosmarinus officinalis essential oil in Tribolium castaneum (Herbst)[END_REF].

In term of surfactant type and amount, [START_REF] Badri | Elaboration of nanoparticles containing indomethacin: Argan oil for transdermal local and cosmetic application[END_REF] pointed out that the amount of polyvinyl alcohol used as surfactant had no significant effect on the average diameter of poly (ε-caprolactone) nanoparticles but at higher concentration (more than 0.1mg/mL), a significant increase was assessed due to the deposition of extra polyvinyl alcohol on the nanoparticle surface. Furthermore, it was reported that the use of span 20 instead of tween 20 gave smaller rosemary EO-loaded nanocapsules, lower polydispersity index and limited loss of the oil during the solvent evaporation step. In the presence of span 20, the hydrophilic lipophilic balance (HLB) was between 12 and 15 (14.3), which was in the range of HLB necessary for rosemary EO nanoemulsion stability [START_REF] Ephrem | Optimisation of rosemary oil encapsulation in polycaprolactone and scale-up of the process[END_REF]. Furthermore, the effect of the ratio between organic and aqueous phase may affect the particle size. Indeed, an increase in argan oil loaded nanoparticles was assessed when increasing the organic to aqueous phase ratio due to the slow diffusion of the organic solvent (acetone) to water resulting slow polymer precipitation and thus, larger pNPs were obtained [START_REF] Badri | Elaboration of nanoparticles containing indomethacin: Argan oil for transdermal local and cosmetic application[END_REF].

Regarding the effect of operating conditions, [START_REF] Badri | Elaboration of nanoparticles containing indomethacin: Argan oil for transdermal local and cosmetic application[END_REF] investigated the effect of stirring speed and organic phase addition rate consisting of poly (ε-caprolactone), acetone, argan oil, indomethacin and span20 on the physicochemical properties of the obtained pNPs.

Results revealed a decrease in particle size by increasing the stirring speed. While, it increases when decreasing the organic phase addition speed due to the difficulty to get a homogenous mixture of phases. Furthermore, [START_REF] Ephrem | Optimisation of rosemary oil encapsulation in polycaprolactone and scale-up of the process[END_REF] studied the influence of the evaporation method on the pNPs properties and rosemary EO loss and found that the evaporation of acetone under normal pressure at room temperature was the best since it avoided heat and low pressure, giving negligible loss of the encapsulated EO.

Recently, a novel form of pNPs was developed called lipid-core nanocapsules which is composed of a mixture of oil and solid lipid surrounded by a polymeric wall [START_REF] Ourique | Lipid-core nanocapsules as a nanomedicine for parenteral administration of tretinoin: development and in vitro antitumor activity on human myeloid leukaemia cells[END_REF]. For instance, the oily core of pNP may consist of a liquid lipid, a mixture of liquid lipids, or a mixture of liquid lipid and solid lipid. The latter concerns a specific form of nanocapsules called lipid-core nanocapsules (Frank et al., 2015). Several research works have been already

published investigated the feasibility to entrap VO into lipid core NPs [START_REF] Almeida | Oil-based nanoparticles containing alternative vegetable oils (grape seed oil and almond kernel oil): Preparation and characterization[END_REF][START_REF] Drozdek | Biocompatible oil core nanocapsules as potential co-carriers of paclitaxel and fluorescent markers : preparation, characterization and bioimaging[END_REF][START_REF] Friedrich | Development and physicochemical characterization of dexamethasone-loaded polymeric nanocapsule suspensions[END_REF][START_REF] Marchiori | Hydrogel containing silibinin-loaded pomegranate oil based nanocapsules exhibits antiinflammatory effects on skin damage UVB radiation-induced in mice[END_REF][START_REF] Rigo | Influence of the type of vegetable oil on the drug release profile from lipid-core nanocapsules and in vivo genotoxicity study[END_REF][START_REF] Weber | Association of borage oil and betamethasone dipropionate in lipid-core nanocapsules: characterization, photostability and in vitro irritation test[END_REF]. In this context, nanoprecipitation technique was efficiently carried out to develop borage oil : betamethasone co-loaded lipid-core nanocapsules with a mean size around 210 nm, negative zeta potential (-16.6mv), low polydispersity index (<0.05) and high EE% (up to 100%) [START_REF] Weber | Association of borage oil and betamethasone dipropionate in lipid-core nanocapsules: characterization, photostability and in vitro irritation test[END_REF]. Furthermore, [START_REF] Rigo | Influence of the type of vegetable oil on the drug release profile from lipid-core nanocapsules and in vivo genotoxicity study[END_REF] studied the influence of the type of VO on the release kinetic of clobetasol propionate, selected as model drug, from the lipid core nanoparticles. Results revealed a biphasic drug release profiles for all the formulations.

After 168 h, the concentration of clobetasol propionate released from the formulation was in the following order: Sunflower oil-pNPs ˂ Soybean oil-pNPs ˂ Rice ban-pNPs. The authors related these results to the consistency indices of the mixture oil : sorbitan monostearate, used as solid lipid; and a greater control of the drug release was observed with higher consistency index of the VO-sorbitan monostearate.

Regarding the nanoparticles stability, [START_REF] Badri | Poly (ε-caprolactone ) nanoparticles loaded with indomethacin and Nigella Sativa L. essential oil for the topical treatment of inflammation[END_REF] investigated the stability of poly (ε-caprolactone) based nanoparticles containing Nigella sativa EO coupled with indomethacin during one month under three different conditions (4°C, 25°C and 40°C). The samples were analyzed at predefined times and results demonstrated no significant change in either size or zeta potential for all the tested particles. Similarly, the photodegradation study of the lipid-core nanocapsules containing borage oil and betamethasone was carried out to demonstrate the ability of nanocapsules in the photoprotection of the drug. In brief, nanoparticles suspensions were placed in transparent quartz cell and exposed to UVC radiation and the total concentration of drug was quantified. Results revealed a degradation of 61% from the nanocapsules suspension at the end of the experiment (10 h), while 58% of drug was degraded in 2 h from drug solution. This confirmed the property of polymeric wall to protect the bioactive molecules [START_REF] Weber | Association of borage oil and betamethasone dipropionate in lipid-core nanocapsules: characterization, photostability and in vitro irritation test[END_REF].

Regarding the scalability and reproducibility of the nanoprecipitation process, it was noticed no significant difference between rosemary EO loaded poly (ε-caprolactone) nanocapsules prepared at small and large scales in term of shape, particle size, polydispersity index zeta potential and EE% [START_REF] Ephrem | Optimisation of rosemary oil encapsulation in polycaprolactone and scale-up of the process[END_REF].

Overall, the nanoprecipitation or solvent displacement method is widely used to develop pNPs for plants oils encapsulation. According to the Table 1, the polymers commonly used to design the polymeric matrix are synthetic polyesters like poly (lactide-co-glycolide) [START_REF] Esfandyari-Manesh | Study of antimicrobial activity of anethole and carvone loaded PLGA nanoparticles[END_REF][START_REF] Iannitelli | Potential antibacterial activity of carvacrol-loaded poly(DL-lactide-co-glycolide) (PLGA) nanoparticles against microbial biofilm[END_REF][START_REF] Sousa | Nanostructured systems containing babassu (Orbignya speciosa) oil as a potential alternative therapy for benign prostatic hyperplasia[END_REF], poly (εcaprolactone) [START_REF] Badri | Poly (ε-caprolactone ) nanoparticles loaded with indomethacin and Nigella Sativa L. essential oil for the topical treatment of inflammation[END_REF][START_REF] Christofoli | Insecticidal effect of nanoencapsulated essential oils from Zanthoxylum rhoifolium (Rutaceae) in Bemisia tabaci populations[END_REF][START_REF] Ephrem | Optimisation of rosemary oil encapsulation in polycaprolactone and scale-up of the process[END_REF][START_REF] Jummes | Antioxidant and antimicrobial poly-ε-caprolactone nanoparticles loaded with Cymbopogon martinii essential oil[END_REF][START_REF] Khoobdel | Insecticidal activity of polycaprolactone nanocapsules loaded with Rosmarinus officinalis essential oil in Tribolium castaneum (Herbst)[END_REF], polylactide [START_REF] Liakos | Polylactic acid-lemongrass essential oil nanocapsules with antimicrobial properties[END_REF], Eudragit ® L100 [START_REF] Averina | Encapsulation of alimentary bioactive oils of the Baikal Lake area into pH-sensitive micro-and nanoparticles[END_REF], S100 [START_REF] Averina | Encapsulation of alimentary bioactive oils of the Baikal Lake area into pH-sensitive micro-and nanoparticles[END_REF], L100-55 (Pina-Barrera et al., 2019) and RS100 (El-Asbahani et al., 2015;[START_REF] Froiio | Essential oils-loaded polymer particles: Preparation, characterization and antimicrobial property[END_REF]. Synthetic polymers are more used than natural ones like chitosan [START_REF] Luque-Alcaraz | Enhanced antifungal effect of chitosan/Pepper tree (Schinus molle) essential oil bionanocomposites on the viability of Aspergillus parasiticus spores[END_REF][START_REF] Sotelo-Boyás | Characterization of chitosan nanoparticles added with essential oils. In vitro effect on Pectobacterium carotovorum[END_REF], 2017a, 2017b) and cellulose derivatives [START_REF] Liakos | Cellulose acetate -essential oil nanocapsules with antimicrobial activity for biomedical applications[END_REF][START_REF] Marchiori | Hydrogel containing silibinin-loaded pomegranate oil based nanocapsules exhibits antiinflammatory effects on skin damage UVB radiation-induced in mice[END_REF] because they have higher purity and better reproducibility. The benefits associated to this encapsulation method are rapidity, simplicity, reproducibility, and scalability. Moreover, NPs with narrow size distribution, high EE% and high stability could be obtained. In addition, the use of surfactant or high production energy is avoided. The main drawback of this method in encapsulating plant oils is the use of organic solvents which may be toxic for health.

Ionic gelation

In order to avoid the use of toxic organic solvent or high shear forces, Calco et al. (1997) proposed a novel approach called ionic gelation or coacervation. Alginate, an anionic polysaccharide, and chitosan, a cationic polyelectrolyte, are extensively used for ionic gelation purpose. These polyelectrolytes can interact with crosslinking agents like tripolyphosphate having an opposite charge via electrostatic interaction and aggregate into nanoparticles (J. Yang et al., 2015). The coacervation consists on the transition from liquid to gel state upon complexation between the oppositely charged molecules at determined pH values leading to the formation of nano-sized particles (Nagavarma et al., 2012) (Fig.5.c). A number of studies have been carried out using this technique to encapsulate plant oils, as displayed in Table 1.

Recently, cinnamon EO-loaded chitosan nanoparticles crosslinked with tripolyphosphate were prepared by using coacervation method and the obtained particles owned small average diameter (80-100 nm) with good zeta potential values (-11.2 to -22.4 mV) [START_REF] Liu | Development of poly (lactic acid)/ chitosan fibers loaded with essential oil for antimicrobial applications[END_REF]. In addition, cardamom EO was successfully entrapped into chitosan based nanoparticles with an average particle size ranging between 50 and 100 nm, zeta potential more than +50 mV and a high EE% which was more than 90% [START_REF] Jamil | Encapsulation of cardamom essential oil in chitosan nano-composites : In-vitro efficacy on antibiotic-resistant bacterial pathogens and cytotoxicity studies[END_REF]. Furthermore, Woranuch and his coworker (2013) reported that the thermal stability of eugenol was enhanced by encapsulation in chitosan: tripolyphosphate-nanoparticles. According to some research works depicted in Table 2, the ionic gelation technique may produce microparticles with moderate EE% as compared to the nanoprecipitation process (Feyzioglu and Tornuk, 2016;[START_REF] López-Meneses | Schinus molle L . essential oil-loaded chitosan nanoparticles : Preparation, characterization, antifungal and anti-aflatoxigenic properties[END_REF][START_REF] Sutaphanit | Optimisation of microencapsulation of holy basil essential oil in gelatin by response surface methodology[END_REF][START_REF] Yang | Development and evaluation of novel flavour microcapsules containing vanilla oil using complex coacervation approach[END_REF][START_REF] Zhang | Synthesis and release studies of microalgal oil-containing microcapsules prepared by complex coacervation[END_REF].

Currently, several research works have been reported to investigate the effect of pNPs composition and operating conditions on physicochemical properties of particles prepared by ionic gelation method. The optimization of the type and amount of polymer and crosslinking agent is crucial to develop pNPs with suitable characteristics. In this approach, Carum copticum EO-loaded chitosan nanoparticles were prepared by ionic gelation method using two types of crosslinking agents: tripolyphosphate and hexametaphosphate [START_REF] Esmaeili | In vitro release and biological activities of Carum copticum essential oil (CEO) loaded chitosan nanoparticles[END_REF]. The efficacy of crosslinking agent type and tripolyphosphate concentration on the EE% were evaluated. The particles prepared using hexametaphosphate (0.5% (w/v)) had significantly lower loading capacity and EE% than those prepared using tripolyphosphate (0.5% (w/v)). This was attributed to the ring structure and bigger size of hexametaphosphate which in turn lead to decrease the crosslinking phenomenon. In the same work, different nanoparticles were prepared using different tripolyphosphate concentrations (0.25, 0.5, 0.75 and 1% (w/v)) and results indicated that maximum EE% was obtained with the concentration of 0.5% (w/v). The low value of EE% obtained with the concentration of 0.25% (w/v) was explained by the shortage of tripolyphosphate concentration to crosslink the nanoparticles; while the low values shown with 0.75 and 1% (w/v) tripolyphosphate concentrations were related to the particle shrinkage [START_REF] Esmaeili | In vitro release and biological activities of Carum copticum essential oil (CEO) loaded chitosan nanoparticles[END_REF].

With respect to the polymer effect, the viscosity of chitosan was optimized for fabrication of vanilla oil loaded microcapsules using the coacervation method [START_REF] Yang | Development and evaluation of novel flavour microcapsules containing vanilla oil using complex coacervation approach[END_REF]. Results showed that at low chitosan viscosity, no microcapsules were formed because chitosan at low viscosity could not form hard membrane wall. On the other hand, when using high viscosity chitosan, aggregation problem was observed [START_REF] Yang | Development and evaluation of novel flavour microcapsules containing vanilla oil using complex coacervation approach[END_REF].

Regarding the EO concentration, [START_REF] Hasheminejad | Improving the antifungal activity of clove essential oil encapsulated by chitosan nanoparticles[END_REF] stated that both particle size and zeta potential decreased significantly when increasing clove EO concentration. The reduction in particle size was explained by the great packing of polymer chains, due to the high number of amino groups in chitosan responsible for the interaction with the oil. Additionally, the thermogravimetric analysis performed by [START_REF] Hosseini | Two-step method for encapsulation of oregano essential oil in chitosan nanoparticles : Preparation , characterization and in vitro release study[END_REF] on oregano EO loadedchitosan nanoparticles demonstrated that as the initial EO content increases from 0.1 to 0.8 g/g chitosan, loading capacity increases too from 3 to 8%, but the EE% decreases from 47 to 21%.

This was explained by the saturation of oregano EO loaded into chitosan nanoparticles. The EO concentration was found to affect also the in vitro release profile. Indeed, Hosseini and his coworkers reported that low concentration of oregano EO (0.1 g/g chitosan) leads to burst release (82% of encapsulated EO was released from the nanoparticles within 3 h). While, as oregano EO amount increased, the burst effect was dramatically alleviated and the cumulative release was reduced from 82 to 12% after 3h. This phenomenon was attributed to the fact that chitosan nanoparticles with smaller particle size would have bigger surface-to-volume ratio which may result in fast release of oregano EO adsorbed on their surfaces [START_REF] Hosseini | Two-step method for encapsulation of oregano essential oil in chitosan nanoparticles : Preparation , characterization and in vitro release study[END_REF]. Another factor affecting the release profile was found to be the composition of the encapsulated material. In 2014, Dima et al. investigating the release of Pimenta dioica EO found that chitosan microspheres covered with k-carrageenan are more fragile and exhibit higher swelling degree with zero order release kinetics, as compared to the chitosan : kcarrageenan microspheres hardened by glutaraldehyde crosslinking which show non-Fickian release mechanism [START_REF] Dima | Reprint of " Microencapsulation of essential oil of pimento [ Pimenta dioica ( L ) Merr .] by chitosan / k-carrageenan complex coacervation method[END_REF].

Numerous research works noticed the stability of pNPs produced by ionic gelation method. In 2014, Sutaphanit et al. reported that the encapsulation of holy basil EO into gelatin by simple coacervation method could prevent its volatility and oxidation [START_REF] Sutaphanit | Optimisation of microencapsulation of holy basil essential oil in gelatin by response surface methodology[END_REF]. Indeed, the particles stored under accelerated conditions at 60 0 C for 49 days exhibited small decreases in the holy basil EO retention rate and antioxidant activity [START_REF] Sutaphanit | Optimisation of microencapsulation of holy basil essential oil in gelatin by response surface methodology[END_REF]. Moreover, the stability studies performed on peppermint oil loaded capsules showed that only 7% of the oil was released during the storage of 40 days in cold water [START_REF] Dong | Morphology and release profile of microcapsules encapsulating peppermint oil by complex coacervation[END_REF]. In another work study, jasmine EO nanoparticles exhibited high heatstability against humid heat (80 ∘ C for 7h) [START_REF] Lv | Formation of heat-resistant nanocapsules of jasmine essential oil via gelatin / gum arabic based complex coacervation[END_REF].

On the whole, ionic gelation method is broadly used to encapsulate plants oils when compared to simple emulsion evaporation method. Gelatin [START_REF] Devi | Study of complex coacervation of gelatin A and sodium alginate for microencapsulation of olive oil[END_REF][START_REF] Dong | Morphology and release profile of microcapsules encapsulating peppermint oil by complex coacervation[END_REF][START_REF] Sutaphanit | Optimisation of microencapsulation of holy basil essential oil in gelatin by response surface methodology[END_REF][START_REF] Zhang | Synthesis and release studies of microalgal oil-containing microcapsules prepared by complex coacervation[END_REF], arabic gum [START_REF] Dong | Morphology and release profile of microcapsules encapsulating peppermint oil by complex coacervation[END_REF][START_REF] Lv | Formation of heat-resistant nanocapsules of jasmine essential oil via gelatin / gum arabic based complex coacervation[END_REF][START_REF] Yang | Development and evaluation of novel microcapsules containing poppy-seed oil using complex coacervation[END_REF][START_REF] Zhang | Synthesis and release studies of microalgal oil-containing microcapsules prepared by complex coacervation[END_REF], alginate [START_REF] Devi | Study of complex coacervation of gelatin A and sodium alginate for microencapsulation of olive oil[END_REF][START_REF] Natrajan | Formulation of essential oilloaded chitosan alginate nanocapsules[END_REF] and chitosan (Feyzioglu and Tornuk, 2016;[START_REF] Hosseini | Two-step method for encapsulation of oregano essential oil in chitosan nanoparticles : Preparation , characterization and in vitro release study[END_REF][START_REF] Jamil | Encapsulation of cardamom essential oil in chitosan nano-composites : In-vitro efficacy on antibiotic-resistant bacterial pathogens and cytotoxicity studies[END_REF][START_REF] Liu | Development of poly (lactic acid)/ chitosan fibers loaded with essential oil for antimicrobial applications[END_REF][START_REF] López-Meneses | Schinus molle L . essential oil-loaded chitosan nanoparticles : Preparation, characterization, antifungal and anti-aflatoxigenic properties[END_REF] are the most commonly used wall materials. In addition, tripolyphosphate [START_REF] Hasheminejad | Improving the antifungal activity of clove essential oil encapsulated by chitosan nanoparticles[END_REF][START_REF] Hosseini | Two-step method for encapsulation of oregano essential oil in chitosan nanoparticles : Preparation , characterization and in vitro release study[END_REF][START_REF] Hu | Effect of chitosan nanoparticles loaded with cinnamon essential oil on the quality of chilled pork[END_REF][START_REF] Liu | Development of poly (lactic acid)/ chitosan fibers loaded with essential oil for antimicrobial applications[END_REF][START_REF] Woranuch | Eugenol-loaded chitosan nanoparticles : I . Thermal stability improvement of eugenol through encapsulation[END_REF] and glutaraldehyde [START_REF] Devi | Study of complex coacervation of gelatin A and sodium alginate for microencapsulation of olive oil[END_REF][START_REF] Dima | Reprint of " Microencapsulation of essential oil of pimento [ Pimenta dioica ( L ) Merr .] by chitosan / k-carrageenan complex coacervation method[END_REF][START_REF] Natrajan | Formulation of essential oilloaded chitosan alginate nanocapsules[END_REF][START_REF] Sutaphanit | Optimisation of microencapsulation of holy basil essential oil in gelatin by response surface methodology[END_REF] are widely used as crosslinking agents. The main advantages of ionic gelation method are, in particular; the avoidance of high shear forces and the use of aqueous solvents instead of organic ones.

Moreover, ionic gelation is simple, economic and reproducible. However, moderate EE% and larger particle size were assessed using this method as compared to the nanoprecipitation technique.

Encapsulation in lipid based nanocarriers

Liposomes

Liposomes were first developed for drug delivery purposes by [START_REF] Bangham | Diffusion of univalent ions across the lamellae of swollen phospholipids[END_REF][START_REF] Bangham | Diffusion of univalent ions across the lamellae of swollen phospholipids[END_REF]. Liposomes are vesicles formed by one or more lipid bilayers defining one or several aqueous compartments. They can be classified depending on their size and lamellarity to: i) small unilamellar vesicles (SUV) with a size between 20nm and 100 nm, ii) large unilamellar vesicles (LUV) with a size greater than 100 nm and iii) multilamellar vesicles (MLV) with a size greater than 0.5µm, as demonstrated in Fig. 6 (El-Asbahani et al., 2015). Generally, the liposome bilayer consists of natural and/or synthetic phospholipids like phosphatidylcholline, phosphatidylethanolamine, phosphatidylserine, phosphatidylglycerol and phosphatidylinositol.

Cholesterol may also be incorporated to the lipidic bilayer to reduce the permeability of watersoluble molecules through the membrane and improve its fluidity, and stability [START_REF] Laouini | Preparation , characterization and applications of liposomes : State of the art[END_REF]. Due to the lipophilic character of the liposome bilayer, plant oils like essential or vegetable oils are highly entrapped to enhance their bioavailability and hurdle their physicochemical instability upon exposure to light, oxygen and temperature (El-Asbahani et al., 2015). Several methods have been used to develop liposomes containing plants oils, while the thin film hydration, solvent injection and heating methods were widely used in the last decade.

Fig. 6. Schematic illustration of the techniques used to produce liposomes.

Thin lipid film hydration

Thin lipid film hydration or thin membrane hydration is the first process which was initially used for liposomes production [START_REF] Bangham | Diffusion of univalent ions across the lamellae of swollen phospholipids[END_REF]. A mixture of lipid ingredients was dispersed in organic solvent in a round-bottom flask. Subsequent evaporation of the organic solvent was performed using a rotary evaporator at reduced pressure. Finally, the hydration of the formed lipid film by water or buffer solution under agitation at temperature above the lipid transition temperature allows the formation of MLVs dispersion (Fig. 6.a) [START_REF] Laouini | Preparation , characterization and applications of liposomes : State of the art[END_REF].

Liposome size reduction techniques, such as sonication or extrusion were applied to ensure size reduction and particles uniformity [START_REF] Patil | Novel methods for liposome preparation[END_REF]. Thin hydration method was extensively used to develop plant oils-loaded liposomes, as illustrated in Table 2.

Regarding the size of liposomes prepared by this method, several work studies reported a small average diameter with a spherical shape. [START_REF] Cui | The specific antibacterial activity of liposome-encapsulated clove oil and its application in tofu[END_REF] revealed that clove EO loadedliposomes had small size of 149.2 nm, a high zeta potential (-24.5 mV) with an entrapment efficiency of 20.41%, for 5.0 mg/mL clove oil concentration. Accordingly, Cui et al. (2016) used the same method to limit the volatility of salvia EO by encapsulation in soy lecithin/cholesterol based liposomes. Atomic force microscopy images showed that the obtained liposomes were spherical in shape, uniformly dispersed without any aggregation with an average size ranging from 100 to 700 nm. Furthermore, bergamot EO and its fraction (bergapten) were entrapped in phospholipids based-liposomes using thin lipid hydration process [START_REF] Celia | Anticancer activity of liposomal bergamot essential oil (BEO) on human neuroblastoma cells[END_REF]. The prepared liposomes had an average size of 188.25 and 185.14 nm, a zeta potential of -2.95 and -2.57 mV and a high EE% of 75.0 and 77.0% for bergamot EO and its fraction, respectively [START_REF] Celia | Anticancer activity of liposomal bergamot essential oil (BEO) on human neuroblastoma cells[END_REF].

Several authors have compared the size of empty liposomes to EO-loaded liposomes prepared by thin hydration method. Ge and his coworker (2016) revealed a significant difference in the average size between empty-and Melaleuca alternifolia EO loaded-liposomes.

Empty liposomes had an average size of 142 nm, while loaded liposomes were smaller with size around 75 nm. Similar results were found byYoshida et al. [START_REF] Yoshida | Liposomes incorporating essential oil of Brazilian cherry (Eugenia uniflora L.): Characterization of aqueous dispersions and lyophilized formulations[END_REF]. [START_REF] Risaliti | Liposomes loaded with Salvia triloba and Rosmarinus officinalis essential oils : In vitro assessment of antioxidant , antiinflammatory and antibacterial activities[END_REF] attributed this to the high cohesion package of oil components to the bilayer constituents. On the other hand, [START_REF] Detoni | Evaluation of thermal-oxidative stability and antiglioma activity of Zanthoxylum tingoassuiba essential oil entrapped into multi-and unilamellar liposomes[END_REF] reported no difference in liposomes size between empty and Zanthoxylum tingoassuiba EO-loading MLVs and SUVs, respectively.

Moreover, nerolidol-and cyclodextrin/nerolidol-loaded liposomes prepared by thin lipid hydration method showed larger mean particle size than blank liposomes [START_REF] Azzi | First evaluation of drug-in-cyclodextrin-in-liposomes as an encapsulating system for nerolidol[END_REF].

Cui et al. studying the encapsulation of curry EO in liposomes, revealed that the oil concentration had a positive effect on vesicles size (Cui et al., 2017a). For instance, the vesicles size was increased from 103.86 to 257.36 nm as a consequence of an increase in the oil concentration from 2.0 to 6.0 mg/ml. Similar behavior was pointed for the encapsulation of cinnamon EO in soy lecithin/cholesterol based liposomes prepared by thin hydration method (Cui et al., 2016a). Accompanying the increase of cinnamon oil concentration from 3.0 to 6.0 mg/mL, the vesicles size was progressively increased from 133 to 157 nm. Similar results were also reported when increasing cardamom EO [START_REF] Nahr | Investigation of physicochemical properties of essential oil loaded nanoliposome for enrichment purposes[END_REF], thyme EO (Cui et al., 2017b) and chrysanthemum EO (Lin et al., 2019b).

The liposome size was not only affected by the EO concentration. In fact, [START_REF] Nazari | Garlic essential oil nanophytosomes as a natural food preservative : Its application in yogurt as food model[END_REF] developing garlic EO nanophytosomes by thin hydration method, investigated the effect of the preparation method. For instance, nanophytosomes were a novel lipid based vesicular delivery systems where stable hydrogen bonds are formed between the phosphatidylcholine molecules and nutraceuticals leading to the formation of stable complex [START_REF] Ghanbarzadeh | Nano-phytosome as a potential food-grade delivery system[END_REF]. In this study, MLVs reduction size was performed using three different types of methods: sonication, homogenization and the combination of sonication and homogenization. Results

showed that the combination of two methods produced the smallest liposomes (115 nm) with transparent suspension view. Homogenization produced larger particles than probe sonication method and the average size was around 161 and 135 nm, respectively. Considering the zeta potential, all the prepared phytosomes had lower values (-12.36 to -3.86 mV) than the expected and reported values for soy bean phosphatidylcholine made nanovesicular systems (around -26 mV). This was linked to the interaction between the positively charged allicin (the main component of garlic EO) and the negatively charged phosphate group of phosphatidylcholine [START_REF] Nazari | Garlic essential oil nanophytosomes as a natural food preservative : Its application in yogurt as food model[END_REF]. In another work study, Salari and his colleague (2019) developing rosemary EO loaded-L-α-phosphatidylethanolamine dioleoyl : cholesteryl hemisuccinate liposomes found that sonication method produced smaller liposome than filtration method. The average sizes were 142.5 and 437.2 nm, respectively. Results showed also that increasing the lipid ratio of L-α-phosphatidylethanolamine dioleoyl to cholesteryl hemisuccinate from 3:2 to 7:3 resulted in much larger liposomes with more negative zeta potential.

As there are several types of phospholipids, it is reliable to alter the size, charge and EE%, upon variation of type or addition of new ingredients to the lipid mixture. In this approach, the effect of lipid composition on the EE% of Anethum graveolens EO-loaded liposomes was investigated by [START_REF] Ortan | Studies concerning the entrapment of Anethum graveolens essential oil in liposomes[END_REF]. Liposomes with different lipids; fresh egg yolk, dimiristroylphosphatidyl choline, dipalmitoylphosphatidyl choline, dimiristroylphosphatidyl glycerol and dioleoylphosphatidyl choline, were prepared by thin hydration method. Results showed that oil entrapment varied in this way:

dimiristroylphosphatidyl glycerol (55.2%) ˂ dimiristroylphosphatidyl choline (58.9%) ˂ dioleoylphosphatidyl choline (77%) ˂ dipalmitoylphosphatidyl choline (97%) ˂ fresh egg yolk (98%). Although dipalmitoylphosphatidyl choline showed good entrapment efficiency, its use was difficult as it required high temperature due to its high transition temperature. The authors related the low values of EE% of dioleoylphosphatidyl choline, dimiristroylphosphatidyl glycerol and dimiristroylphosphatidyl choline to their unsaturation.

In addition to the factors mentioned above, other parameters may affect the physicochemical properties of liposomes prepared by thin hydration process. In this context, Plackett-Burman design was applied in order to investigate the effect of the mass ratio of phosphatidylcholine and cholesterol, tree tea EO concentration, tween 80 concentration, hydration medium pH, temperature, sonication time and power on physicochemical properties of tree tea EO-loaded liposomes [START_REF] Ge | of tea tree oil-loaded liposomal formulation using response surface methodology D. of tea tree oil-loaded liposomal formulation using response surface methodology[END_REF]. Results revealed that only three factors (the ratio of phosphatidylcholine and cholesterol, EO concentration and tween 80) exhibited a significant impact on the entrapment efficiency of tree tea EO. Increasing the lipid ratio with EO amount and decreasing tween 80 had a positive effect on EO encapsulation efficiency. Good EE% (97.18%) was obtained with the following parameters: the mass ratio of fresh egg yolk and cholesterol (5:51); EO concentration (1.21%); tween 80 concentration (0.79%); pH 7.4; temperature (55 °C); sonication time (15 min) and sonication power (300w) [START_REF] Ge | of tea tree oil-loaded liposomal formulation using response surface methodology D. of tea tree oil-loaded liposomal formulation using response surface methodology[END_REF].

Regarding the stability of EO loaded in liposomes, [START_REF] Liolios | Liposomal incorporation of carvacrol and thymol isolated from the essential oil of Origanum dictamnus L . and in vitro antimicrobial activity[END_REF] Liposomes +Carvacrol : Thymol (392°C). One can conclude that carvacrol and thymol presented better antioxidant action when encapsulated than when in pure form. The antioxidant activity of empty liposomes is lower than that of oil loaded-liposome, suggesting that the liposome membranes were stabilized by the link of the lipophilic compounds with lipid bilayers [START_REF] Liolios | Liposomal incorporation of carvacrol and thymol isolated from the essential oil of Origanum dictamnus L . and in vitro antimicrobial activity[END_REF].

Beyond EO, liposomes can potentially enable the encapsulation of VO and their derivatives, as illustrated in Table 3. Recently, numerous studies have been investigated to encapsulate fatty acids in liposomes. Among the several polyunsaturated fatty acids (PUFAs), dietary ω3 like eicosapentaenoic and docosahexaenoic acids have been extensively investigated for their beneficial effects [START_REF] Hadian | A review of nanoliposomal delivery system for stabilization of bioactive omega-3 fatty acids[END_REF]. [START_REF] Alaarg | Docosahexaenoic acid liposomes for targeting chronic inflammatory diseases and cancer : an in vitro assessment[END_REF] developed docosahexaenoic acid-loaded liposomes by thin hydration method. The obtained liposomes exhibited small average diameter around 100 nm, narrow size distributions, negative zeta potential (15.7 ± 2.5mv) and high EE% of 81.35 %. Moreover, eicosapentaenoic and docosahexaenoic acids were entrapped in nanoliposomes (i.e. nanoscale lipid vesicles) developed by thin hydration followed by either extrusion ultrasonic irradiation; bath sonication; probe sonication; or combined probe and bath sonication [START_REF] Hadian | Formulation , characterization and optimization of liposomes containing eicosapentaenoic and docosahexaenoic acids ; A methodology approach[END_REF]. Results showed that probe sonication produced liposomes with higher EE% for both investigated fatty acids. Results displayed also that EE% differs form a VO to another for liposomes prepared in the same experimental conditions. Indeed, the EE% value was higher for docosahexaenoic acid than for eicosapentaenoic acid. This was ascribed to the fact that docosahexaenoic acid may change the physical properties of 1, 2-dipalmitoyl-sn-glycero-3-phosphocholine bilayer, as it would provide a tightly pack conformation because of the coiled configuration [START_REF] Hadian | Formulation , characterization and optimization of liposomes containing eicosapentaenoic and docosahexaenoic acids ; A methodology approach[END_REF].

In overall, thin hydration method is widely employed to develop plant oils loaded liposomes due to its simplicity. Several phospholipids are used in the literature including soybean phosphatidylcholine (Ge & Ge, 2016;[START_REF] Ge | of tea tree oil-loaded liposomal formulation using response surface methodology D. of tea tree oil-loaded liposomal formulation using response surface methodology[END_REF][START_REF] Khatibi | Effect of nanoliposomes containing Zataria multiflora Boiss . essential oil on gene expression of Shiga toxin 2 in Escherichia coli O157 : H7[END_REF][START_REF] Nazari | Garlic essential oil nanophytosomes as a natural food preservative : Its application in yogurt as food model[END_REF][START_REF] Rasti | Comparative study of the oxidative and physical stability of liposomal and nanoliposomal polyunsaturated fatty acids prepared with conventional and Mozafari methods[END_REF][START_REF] Wang | Evaluation of carboxymethyl chitosan coated liposomes containing fish oil[END_REF], dipalmitoyl phosphatidylcholine [START_REF] Detoni | Evaluation of thermal-oxidative stability and antiglioma activity of Zanthoxylum tingoassuiba essential oil entrapped into multi-and unilamellar liposomes[END_REF], egg phosphatidylcholine [START_REF] Saffari | Terpene-loaded liposomes and isopropyl myristate as chemical permeation enhancers toward liposomal gene delivery in lung cancer cells ; A comparative study[END_REF], phospholipon ® 90G [START_REF] Risaliti | Liposomes loaded with Salvia triloba and Rosmarinus officinalis essential oils : In vitro assessment of antioxidant , antiinflammatory and antibacterial activities[END_REF]. Cholesterol is the most used fluidifying agent (Alikhani-Koupaei, 2015; H. (Cui et al., 2017a(Cui et al., , 2017b(Cui et al., , 2016a(Cui et al., , 2016b[START_REF] Cui | The specific antibacterial activity of liposome-encapsulated clove oil and its application in tofu[END_REF]Lin et al., 2019b[START_REF] Lin | Improving the stability of thyme essential oil solid liposome by using β -cyclodextrin as a cryoprotectant[END_REF] were incorporated as surfactants.

Using this method, heterogeneous vesicles of large sizes may be produced which requires additional steps like sonication and extrusion to reduce and homogenize the vesicle size and thus, the process consumes more time. Besides, thin hydration method is difficult to scale up and requires organic solvents which in turn represent the major drawback. In fact, their residues may remain in the final liposome preparation resulting in potential toxicity and reduced stability of the lipid vesicles [START_REF] Cortesi | Preparation of liposomes by reverse-phase evaporation using alternative organic solvents[END_REF][START_REF] Vemuri | Preparation and characterization of liposomes as therapeutic delivery systems: a review[END_REF].

Solvent injection

The solvent injection method, firstly described in 1973 [START_REF] Batzri | Single bilayer liposomes prepared without sonication[END_REF], implies the dissolution of the lipid into an organic phase such as ethanol or ether, followed by the injection of the lipid solution into aqueous solution resulting in liposomes dispersion [START_REF] Laouini | Preparation , characterization and applications of liposomes : State of the art[END_REF]. After that, the organic solvent was evaporated under reduced pressure (Fig.

6.b).

This technique is widely used for plant oil encapsulation, as demonstrated in Table 2. The solvent injection' main feature is that narrow size distribution of submicron liposomes (under 100 nm) could be produced without extrusion or sonication [START_REF] Stano | Novel camptothecin analogue (gimatecan)-containing liposomes prepared by the ethanol injection method[END_REF]. Moreover, compared with thin hydration method, the ethanol injection technique was found to be scalable.

In fact, clove EO-liposomes were successfully scaled-up using a membrane contactor (600ml) and a pilot plant (3L) (Sebaaly et al., 2015a). Furthermore, various eugenol-and clove EOliposomes were prepared at laboratory (ethanol injection) and large scale (membrane contactor): free hydroxypropyl-β-cyclodextrin loaded liposomes; drug in hydroxypropyl-βcyclodextrin in liposomes (DCL) and DCL2 obtained by double loading technique, where the drug is added in the organic phase and the inclusion complex in the aqueous phase (Sebaaly et al., 2016a). Results showed that eugenol and clove EO loaded DCL and DCL2 developed at large scale had a mean size similar to those obtained by laboratory scale. Besides, Eugenol and clove EO loaded DCL and DCL2 had a mean particle size significantly smaller than that of free hydroxypropyl-β-cyclodextrin liposomes containing either eugenol or clove EO at both laboratory and large scales. This was explained by the complete incorporation of the aromatic cycle of eugenol inside the hydrophobic cavity of hydroxypropyl-β-cyclodextrin, resulting in limit interaction between eugenol and lipidic bilayers. Regarding the polydispersity index and zeta potential, no difference was assessed between all the tested liposomes.

Currently, several studies have been reported to investigate the effect of liposome composition and operating conditions on physicochemical properties of liposomes prepared by ethanol injection method [START_REF] Hammoud | New findings on the incorporation of essential oil components into liposomes composed of lipoid S100 and cholesterol[END_REF][START_REF] Rushmi | The impact of formulation attributes and process parameters on black seed oil loaded liposomes and their performance in animal models of analgesia[END_REF]Sebaaly et al., 2016b).

The effect of oil concentration, injection rate, stirring speed on the average diameter of black seed oil-liposomes was studied [START_REF] Rushmi | The impact of formulation attributes and process parameters on black seed oil loaded liposomes and their performance in animal models of analgesia[END_REF]. Results showed that liposomes decrease in size from 520.70 to 51.48 nm after oil incorporation. As the concentration of oil increases from 0.17 to 0.67% v/v, liposomes size reduced significantly due to the antioxidant activity of the oil which could decrease phospholipid bilayer oxidation, preventing liposomes growth; while, no change in average size of liposomes was noticed upon further increase in oil (0.67% v/v). Thus, the oil concentration of 0.67% v/v was found to be optimum for its antioxidant activity. Results showed also that small sized liposomes were formed under 1mL/min injection rate and 2200 rpm stirring speed. Low injection rates result in faster lipids oxidation while high rates may cause a variable distribution of particle size. Similar results were already reported (Sebaaly et al., 2016b). In regards of the phospholipid:cholesterol ratio effect, the EE% was improved from 39.8 to 49.9 % after increasing the ratio of egg extract to cholesterol from 3:1 to 3:2 [START_REF] Rushmi | The impact of formulation attributes and process parameters on black seed oil loaded liposomes and their performance in animal models of analgesia[END_REF]. This was related to the fact that cholesterol may reduce the flexibility and mobility of lipidic layer which in turn lead to enhance liposomes stability.

Moreover, another study performed by [START_REF] Hammoud | New findings on the incorporation of essential oil components into liposomes composed of lipoid S100 and cholesterol[END_REF] spotlighted that the type of encapsulated EO affects significantly the phospholipid and cholesterol incorporation rates into the lipid layer. Lower phospholipids incorporation rates were observed when encapsulating isoeugenol, pulegone or thymol. While, high cholesterol incorporation rates were measured in presence of estragole or terpineole. Additionally, the oil entrapment efficiency was found to be affected by the chemical structure of encapsulated EO. In fact, EO bearing hydroxyl groups in their structure are more greatly to fluidize the lipid layer than those without a hydroxyl group leading to higher EE%. The authors concluded that EO bearing hydroxyl groups had low aqueous solubility with low Henry constant value and higher liposomal EE% [START_REF] Hammoud | New findings on the incorporation of essential oil components into liposomes composed of lipoid S100 and cholesterol[END_REF].

Regarding the stability of liposomes prepared by ethanol injection process, Liu et al.

(2016) investigated the stability of galanga EO-loaded liposomes at low temperature (4°C) and dark conditions and results revealed minor change in mean particle size and polydispersity index. Furthermore, the photostability of eugenol in aqueous solution and in liposome formulations (Phospholipon 80H, Phospholipon 90H and Lipoid S100) was investigated under UV light irradiation for 96hours (Sebaaly et al., 2015b). Results revealed that liposomes formulations protect eugenol more than aqueous solutions. The percentages of remaining eugenol were 58, 82, 91 and 95% for aqueous solution, Phospholipon 80H-, 90H-and S100liposomes, respectively. The highest value of remaining eugenol for lipoid S100 was related to the flexibility of the membrane resulting in a deep insertion of eugenol into the lipid bilayer leading to better protection from any UV light effect (Sebaaly et al., 2015b).

Despite using ethanol injection for EO encapsulation in liposomes, a few reports have been published during the last decade regarding the encapsulation of VO. Recently, [START_REF] Huang | Liposome-chitosan hydrogel bead delivery system for the encapsulation of linseed oil and quercetin: Preparation and in vitro characterization studies[END_REF] developed co-loaded linseed oil with quercetin in liposomes with the aim of enhancing their solubility and stability. The produced liposomes owned a spherical shape with a small average size (262.2 nm). In 2019, Bai and his coworkers investigated the effect of different coix seed oil: β-carotene ratios on the physiochemical properties, stability and antioxidant activity of coix seed oil : β-carotene co-loaded-liposomes (C. Bai et al., 2019).

Results showed that by increasing coix seed oil, the EE% of β-carotene in the liposomes decreased. The values of EE% for 1:1, 1:5, and 1:10, β-carotene:coix seed oil liposomes were 83.8, 81.3, and 80.8 %, respectively, which were slightly lower than that of liposomes containing β-carotene alone (86.0%). This was ascribed to the ability of coix seed oil to compete for the available hydrophobic domains within the phospholipid bilayers.

To sum up, ethanol injection method is widely employed for plant oils encapsulation as it is simple, easy to scalable and it does not require any additional process for vesicle size reduction. According to the previous work studies, phospholipon ® 90H (Sebaaly et al., 2016a(Sebaaly et al., , 2016b)), phospholipon ® 80H (Sebaaly et al., 2016b), lipoid ® S100 [START_REF] Hammoud | New findings on the incorporation of essential oil components into liposomes composed of lipoid S100 and cholesterol[END_REF]Sebaaly et al., 2016b) and egg phospholipids (C. Bai et al., 2019;[START_REF] Rushmi | The impact of formulation attributes and process parameters on black seed oil loaded liposomes and their performance in animal models of analgesia[END_REF] are widely used as bilayer forming lipids. Ethanol injection method suffers from several drawbacks including continuous exposure of plant oils to high temperature and organic solvents which may affect both the safety and stability of the liposomes [START_REF] Nkanga | General perception of liposomes : Formation, manufacturing and applications[END_REF].

Heating method

The heating method, called also Mozafari method, was first developed in 2005. It is known to be the most attractive method for liposomes preparation due to its organic solvent/detergents free characteristics [START_REF] Mozafari | A new technique for the preparation of non-toxic liposomes and nanoliposomes: The heating method[END_REF]. In this technique, lipids are hydrated in the presence of hydrating agent (glycerin or propylene glycol) and heated at 40-120°C (at the temperature which is above the transition temperature of the phospholipids) depending on the properties of the ingredients, the presence or absence of cholesterol, and the type of material to be entrapped (Fig. 6.c) [START_REF] Mozafari | Encapsulation of food ingredients using nanoliposome technology[END_REF].

Currently, Mozafari method is widely used to encapsulate VO and polyunsaturated fatty acids (Table 2). When compared to thin hydration process, Mozafari method produce liposomes with higher stability. Rsati et al. ( 2012) investigated the difference between the oxidative stability of liposomes (before sonication) and nanoliposomes (after sonication) produced by Mozafari and conventional thin hydration techniques. For both methods, polyunsaturated fatty acids entrapment efficiency values of nanoliposomes were higher than those of liposomes. Authors related this result to the fact that size reduction increases the surface area of the liposomes resulting in increasing the contact and bond between the fatty acids and phospholipids in the bilayers. Moreover, liposomes prepared by Mozafari process showed higher physical stability than those prepared by conventional method [START_REF] Rasti | Comparative study of the oxidative and physical stability of liposomal and nanoliposomal polyunsaturated fatty acids prepared with conventional and Mozafari methods[END_REF]. In another work study, the effect of formulation strategies on phytosterol, extracted from canola oil, loaded-liposomes was investigated [START_REF] Poudel | Development and characterization of liposomal formulations containing phytosterols extracted from canola oil deodorizer distillate along with tocopherols as food additives[END_REF]. The results showed that Mozafari method produce liposomes with high average size (260 nm) as compared to those obtained by thin film hydration homogenization (186 nm) and thin film hydration ultrasonication (196 nm).

This result was attributed to the high shear force and cavitation involved in size reduction during the ultrasonication and homogenization process; while in Mozafari method, less intense magnetic stirring will probably yield to larger particles. In term of polydispersity index and zeta potential, no difference was found for all the formulations [START_REF] Poudel | Development and characterization of liposomal formulations containing phytosterols extracted from canola oil deodorizer distillate along with tocopherols as food additives[END_REF].

Like the methods discussed above, Mozafari method was affected by several operating conditions. In 2013, Rasti et al. investigated the effect of shear rate, mixing and sonication times on colloidal properties of polyunsaturated fatty acids (docosahexaenoic acid and eicosapentaenoic acid) nanoliposomes [START_REF] Rasti | Optimization on preparation condition of polyunsaturated fatty acids nanoliposome prepared by Mozafari method[END_REF]. In their study, response surface methodology was applied to predict the optimum levels of liposome preparation condition producing maximum EE% and minimum average size. According to ANOVA analysis, all the independent variables and their interactions were found significant; while, the main significant effect on liposome size and EE% was found to be the shear rate. After optimizing the operating parameters; shear rate (795 rpm), mixing time (60 min) and sonication time (10 min), the nanoliposome exhibited an average diameter of 81.4nm with an EE% of 100% [START_REF] Rasti | Optimization on preparation condition of polyunsaturated fatty acids nanoliposome prepared by Mozafari method[END_REF].

Besides using heating method to encapsulate VO in liposomes, no report was found regarding the encapsulation of EO maybe due to their high sensitivity and volatility upon exposure at high temperature. Thus, this technique is not suitable for thermosensitive bioactive agents. In closing, Mozafari method showed to be a fast, simple, scalable, and non-toxic technique for liposome preparation with high EE%. In addition, the obtained liposomes can be freely used without any further sterilization treatments as they were prepared under heating conditions which in turn could minimize both formulation timing and complexity (

Solid lipid nanoparticles and nanostructured lipid carriers

Solid lipid nanoparticles (SLN) are other lipid-based carriers that have emerged as they combine the benefits of liposomes and polymeric nanoparticles [START_REF] Sarangi | Solid lipid nanoparticles-A review[END_REF].

Solid lipid nanoparticles, developed since 1990, are suspensions of nanosized solid lipid particles dispersed in an aqueous media [START_REF] Patel | Development & screening approach for lipid nanoparticle: A review[END_REF]. There are composed of surfactants and a lipid matrix that acquires a solid-state lipid at ambient temperature [START_REF] Bayón-Cordero | Application of solid lipid nanoparticles to improve the efficiency of anticancer drugs[END_REF]. The commonly used materials to structure the lipid core are fatty acids (stearic acid, palmitic acid, decanoic acid and benzoic acid), triacylglycerols (trimyristin, trilaurin, tristearin and tripalmitin) and acyl glycerols (glycerol monostearate, glycerol palmitostearate and glycerol benzoate). These lipids are characterized by their purity, low price, safety and biodegradability. In the other hand, phospholipids (phosphatidylcholine, soy and egg lecithins), poloxamer, pluronic ® F127, bile salts, tween 80 and polyvinyl alcohol are example of commonly used surfactants [START_REF] Kaliamurthi | Insight on solid lipid nanoparticles: characterization and application in diabetes mellitus[END_REF].

In the aim of enhancing the loading capacity of SLN, a second generation of lipid nanoparticles was developed in 1999; so called nanostructured lipid carriers (NLC) in which the matrix is composed not only of a solid lipid, but of a blend of a solid and a liquid lipid oil, as illustrated in Fig. 7. These carriers may provide an additional space for the loading of bioactive agents, improving in this way the amount of the active compounds entrapped and minimizing the probability of expulsion from the lipid phase [START_REF] Patel | Development & screening approach for lipid nanoparticle: A review[END_REF].

Considering the delivery of plant oil, the main reason to use SLN or NLC as nanocarriers is the improvement of entrapment efficiency. Since the oils are mostly lipophilic, they present a good miscibility with the lipid matrix, resulting high amount of oil could be entrapped [START_REF] Falcao | Chapter 23: Challenges in development of essential oil nanodelivery systems and future prospects[END_REF]. In addition, these lipid-based carriers protect the labile and sensitive oil components from chemical, photochemical or oxidative degradation, due to the immobilization by solid lipids. Different methods are employed to produce SLN, however, high pressure homogenization and high-speed homogenization (ultrasonication) are commonly used due to their simplicity and facility of scaling up.

High pressure homogenization

The high-pressure homogenization method was extensively used to encapsulate plant oils in SLN since it produces particles with small size and higher homogeneity. Using a highpressure homogenizer, liquids were pushed with high pressure (100-2000 bar) through a narrow gap (micron size) creating fluid acceleration over a very short distance at very high viscosity of over 1000 km/h which in turn result in disrupting the particles down to submicron range [START_REF] Garud | Solid lipid nanoparticles (SLN): Method , characterization and applications[END_REF].

Using the high-pressure homogenization to encapsulate plants oils, the lipid is heated at 5 to 10°C above its melting point, and the oil is dissolved within (Fig. 7.a). After that two approaches are involved: hot or cold homogenization. In hot homogenization, hot aqueous surfactant solution is dispersed with the plant oil-lipid melt under stirring at the same temperature creating the pre-emulsion. The resultant pre-emulsion was pushed through a piston-gap homogenizer creating a hot oil-in-water (O/W) nanoemulsion which is cooled after at room temperature allowing the crystallization of the lipid and the formation of SLN.

Using the cold homogenization approach the oil-lipid melt was cooled down creating solid lipid microparticles that are dispersed after in a cold aqueous surfactant solution forming a pre-suspension. The subsequent homogenization of this pre-suspension creates SLN (Fig. 7.b). Several studies have been already published investigating the use of high-pressure homogenization process to encapsulate plant oils (see Table 3).

Regarding the size of SLN prepared by this technique, numerous research works reported a small average diameter with good stability and high EE%. For example, SLN containing frankincense and myhrr EO in a ratio 1:1 were developed using hot homogenization process by [START_REF] Wang | Preparation and characterization of solid lipid nanoparticles loaded with frankincense and myrrh oil[END_REF]. An average mean size of 113.3 nm, a zeta potential of -16.8 mV and an EE% of 80.60% were assessed for the obtained SLN. The same process was used to prepare SLN encapsulating the VO: copaiba oil with and without allantoin which is widely used in cosmetology for its keratolytic, moisturizing, soothing and wound healing properties [START_REF] Svetlichny | Solid lipid nanoparticles containing copaiba oil and allantoin : development and role of nanoencapsulation on the antifungal activity[END_REF]. The dynamic light scattering analysis revealed an average particle size of 126.06 nm and 118.63 nm for the copaiba oil-loaded SLN and copaiba oil:

allantoin-co-loaded SLN, respectively.

Concerning the stability of SLN, previous works highlighted their efficiency in preserving the quality of encapsulated oil during long-term storage as compared to unencapsulated-form [START_REF] Tian | Preparation and characterization of citral-loaded solid lipid nanoparticles[END_REF][START_REF] Zielinska | Alpha-Pinene-loaded solid lipid nanoparticles dispersion analysis[END_REF]. [START_REF] Tian | Preparation and characterization of citral-loaded solid lipid nanoparticles[END_REF] reported that SLN can enhance the stability of citral in acidic surroundings. Gas-chromatography analysis showed that after 12 days storage, 67% of citral remained in the citral loaded-SLN formulations, while only 8% remained in the control. In addition, the overall flavour of the degradation products generated from citral-SLN were assessed and results demonstrated that the offflavours had little effect on the whole flavour of citral-SLN in the system sample as compared with the control [START_REF] Tian | Preparation and characterization of citral-loaded solid lipid nanoparticles[END_REF].

Several factors such as the kind of lipid, surfactant and the operating process conditions could influence the physicochemical properties of the particles obtained by high-pressure homogenization. In this context, [START_REF] Mai | Development of solid lipid nanoparticles of Gac (Momordica cocochinensis Spreng) oil by nanoemulsion technique[END_REF] investigated the influence of homogenization conditions on gac fruit EO-loaded SLN prepared by hot and cold homogenization. Results

showed that increasing hot homogenization speed from 5000 to 10000 rpm was accompanied with a decrease in particle size from 3297 to 201 nm. However, further increase in speed leads to increase the particle size due to the fact that the oil particles are more likely to collide and aggregate with others. Concerning hot homogenization time, short time was found not enough for active ingredient encapsulation while more homogenization time result in small particles which in turn lead to reduce the volume containing active ingredients [START_REF] Mai | Development of solid lipid nanoparticles of Gac (Momordica cocochinensis Spreng) oil by nanoemulsion technique[END_REF].

In another work study, the impact of the surfactant content, the ratio of citral to lipid, and their total content on the physicochemical characteristics of citral-loaded SLN has been explored [START_REF] Tian | Preparation and characterization of citral-loaded solid lipid nanoparticles[END_REF]. As the surfactant amount increases the EE% decreases due to the fact that the surface of the formed SLN was not large enough to absorb the excess of surfactant which in turn form micelles, resulting a partitioning phenomenon of citral between micelles and SLN; therefore, a decrease in entrapment efficiency was noticed. Results revealed also an increase in particle size and a decrease in EE% when increasing the content of the mixture citral : glyceryl monostearate, used as lipid matrix, from 1 to 5%. The increase in the content of citral : lipid leads to increase the viscosity of the system which in turn reduce the efficiency of the high-pressure homogenization process to decrease the particle size. Additionally, too much citral and lipid cannot be emulsified when the surfactant content is kept constant this is why the EE% decreased. The same behavior of EE% was observed when increasing the ratio of citral to glycerol monostearate. In fact, the excess of citral cannot be entrapped when the content of the mixture citral : lipid was kept constant [START_REF] Tian | Preparation and characterization of citral-loaded solid lipid nanoparticles[END_REF].

In recent years, NLC were introduced to bypass the potential problems associated with the use of SLN. They were widely used for plant oils encapsulation, as depicted in Table 3.

The main feature of these nanocarriers is to enhance the drug loading and prevent drug expulsion during long term storage [START_REF] Sailaja | Formulation of solid lipid nanoparticles and their applications[END_REF] and this was confirmed by several research works. In 2019, using the high-pressure homogenization technique, Miranda and his colleagues developed Ridolfia segetum EO loaded-NLC with a small particle size (148.1 nm), a high zeta potential (16.3 mV) with excellent loading capacity (EE%=100%) [START_REF] Miranda | Nanostructuring lipid carriers using Ridolfia segetum (L.) Moris essential oil[END_REF]. In another research work, NLC containing sucupira EO produced by hot homogenization process owning an average diameter of 143 nm with an EE% of 99.98% [START_REF] Vieira | Sucupira oil-loaded nanostructured lipid carriers (NLC): Lipid screening, factorial design, release profile, and cytotoxicity[END_REF].

Another characteristic intended by using either SLN or NLC as plant oils carrier is providing a controlled released pattern. For this context, in vitro release profile of sucupira oil from NLC was assessed by means of Franz glass diffusion cells and the recorded release profile was fitted into four mathematical models i.e., zero order, first order, Higuchi and Korsmeyer-Peppas [START_REF] Vieira | Sucupira oil-loaded nanostructured lipid carriers (NLC): Lipid screening, factorial design, release profile, and cytotoxicity[END_REF]. Results showed that the release profile of sucupira oil followed a sustained manner over the course of 8 h. About 17.5% was released within the first hour, while the cumulative amount reached 30% at the end of the 8 h [START_REF] Vieira | Sucupira oil-loaded nanostructured lipid carriers (NLC): Lipid screening, factorial design, release profile, and cytotoxicity[END_REF]. Results showed also that the best model describing the release of sucupira oil from NLC was the first order with a regression coefficient close to 1. In contrary to SLN, the release profile of plant oils from NLC does not follow Higuchi or Korsmeyers-Peppas model. Indeed, the release was governed by sucupira oil concentration inside the particles rather than the physicochemical properties of the carriers and this was expected as NLC are made of blend of solid and liquid lipids. Higuchi and Korsmeyers-Peppas are typically followed in the case of SLN formulations as these have a higher degree of crystallinity which controls better the release profile.

With respect to vegetable oils, NLC were employed for co-delivery of VO with another bioactive molecule [START_REF] Badea | Use of various vegetable oils in designing photoprotective nanostructured formulations for UV protection and antioxidant activity[END_REF][START_REF] Lacatusu | Lipid nanocarriers based on natural oils with high activity against oxygen free radicals and tumor cell proliferation[END_REF][START_REF] Rahman | Zerumbone-loaded nanostructured lipid carriers : preparation, characterization, and antileukemic effect[END_REF][START_REF] Rahman | Acute toxicity study of zerumbone-loaded nanostructured lipid carrier on BALB/c mice model[END_REF][START_REF] Sidding | Thymoquinone-loaded nanostructured lipid carriers : preparation, gastroprotection, in vitro toxicity, and pharmacokinetic properties after extravascular administration[END_REF]. The benefit of these nanocarriers is that the VO can complement or even enhance the biological activity of the synthetic drug [START_REF] Lacatusu | Lipid nanocarriers based on natural oils with high activity against oxygen free radicals and tumor cell proliferation[END_REF]. For this context, diethylamino hydroxybenzoyl hexyl benzoate used as UVA filter was co-encapsulated with various vegetable oils and their combinations (pomegranate seed oil, wheat germ oil, blackcurrant seed oil, sesame seed oil, carrot root oil, raspberry seed oil and rice bran oil) in NLC by high pressure homogenization method in order to enhance its antioxidant activity and UV protection performance [START_REF] Badea | Use of various vegetable oils in designing photoprotective nanostructured formulations for UV protection and antioxidant activity[END_REF]. All the prepared NLC owned a mean particle size in the range of 108 to 145 nm with narrow size distribution, high zeta potential ranging from -34.4 to -44.3 mV and an entrapment efficiency between 51 and 70% [START_REF] Badea | Use of various vegetable oils in designing photoprotective nanostructured formulations for UV protection and antioxidant activity[END_REF].

In another work study, in the aim of enhancing the anti-inflammatory properties, olive oil was co entrapped with thymoquinone in NLC and the resultant particles owned an average diameter around 75 nm with negative zeta potential of -31 mV [START_REF] Sidding | Thymoquinone-loaded nanostructured lipid carriers : preparation, gastroprotection, in vitro toxicity, and pharmacokinetic properties after extravascular administration[END_REF]. Olive oil was further encapsulated in hydrogenated palm oil-NLC for co-delivery with synthetic drug purpose. The resultant particles had a mean diameter, polydispersity index, zeta potential, specific surface area, and crystallinity index of 61.14 nm, 0.461, -25.4 mV, 49.07 m 2 and 27.12% respectively [START_REF] How | Characterization and cytotoxicity of nanostructured lipid carriers formulated with olive oil, hydrogenated palm oil, and polysorbate 80[END_REF].

Besides the synthesized drugs, VO may be co-encapsulated with EO in NLC. For instance, [START_REF] Lacatusu | Lipid nanocarriers based on natural oils with high activity against oxygen free radicals and tumor cell proliferation[END_REF] highlighted the possible blend of plant and animal oils -grape seed oil or fish oil with laurel leaf EO in NLC. The mean average diameter of obtained NLC reduces after increase of grape seed oil or fish oil content. This was ascribed to the role of the long fatty chains of these oils which lead to a more confined lipid core.

On the whole the high-pressure homogenization technique is largely employed thanks to its benefits including low cost, good scalability and high stability of particles. While, with respect to the encapsulation of plant oils hot homogenization is more used as compared to the cold homogenization method. Lipids like tristearin [START_REF] Salminen | Tuning of shell thickness of solid lipid particles impacts the chemical stability of encapsulated x-3 fish oil[END_REF], n-hexadecyl palmitate [START_REF] Lacatusu | Lipid nanocarriers based on natural oils with high activity against oxygen free radicals and tumor cell proliferation[END_REF], myritol ® 318 (caprylic/capric triglyceride) [START_REF] Lacatusu | Lipid nanocarriers based on natural oils with high activity against oxygen free radicals and tumor cell proliferation[END_REF], compritol ® 888 ATO [START_REF] Wang | Preparation and characterization of solid lipid nanoparticles loaded with frankincense and myrrh oil[END_REF], glyceryl monolinoleate [START_REF] Shi | Formulation design, preparation, and in vitro and in vivo characterizations of β -elemene-loaded nanostructured lipid carriers[END_REF][START_REF] Tian | Preparation and characterization of citral-loaded solid lipid nanoparticles[END_REF], oleoyl macrogolglycerides [START_REF] Shi | Formulation design, preparation, and in vitro and in vivo characterizations of β -elemene-loaded nanostructured lipid carriers[END_REF], lipoid ® S100 [START_REF] Sidding | Thymoquinone-loaded nanostructured lipid carriers : preparation, gastroprotection, in vitro toxicity, and pharmacokinetic properties after extravascular administration[END_REF], cetyl palmitate [START_REF] Svetlichny | Solid lipid nanoparticles containing copaiba oil and allantoin : development and role of nanoencapsulation on the antifungal activity[END_REF] and glycerol monostearate [START_REF] Shi | Formulation design, preparation, and in vitro and in vivo characterizations of β -elemene-loaded nanostructured lipid carriers[END_REF] are usually used to structure either SLN or NLC. Soybean lecithin [START_REF] Salminen | Tuning of shell thickness of solid lipid particles impacts the chemical stability of encapsulated x-3 fish oil[END_REF][START_REF] Wang | Preparation and characterization of solid lipid nanoparticles loaded with frankincense and myrrh oil[END_REF], tween 80 [START_REF] Shi | Formulation design, preparation, and in vitro and in vivo characterizations of β -elemene-loaded nanostructured lipid carriers[END_REF][START_REF] Sidding | Thymoquinone-loaded nanostructured lipid carriers : preparation, gastroprotection, in vitro toxicity, and pharmacokinetic properties after extravascular administration[END_REF][START_REF] Svetlichny | Solid lipid nanoparticles containing copaiba oil and allantoin : development and role of nanoencapsulation on the antifungal activity[END_REF][START_REF] Wang | Preparation and characterization of solid lipid nanoparticles loaded with frankincense and myrrh oil[END_REF], tween 20 [START_REF] Badea | Use of various vegetable oils in designing photoprotective nanostructured formulations for UV protection and antioxidant activity[END_REF][START_REF] Lacatusu | Lipid nanocarriers based on natural oils with high activity against oxygen free radicals and tumor cell proliferation[END_REF], span 80 [START_REF] Mai | Development of solid lipid nanoparticles of Gac (Momordica cocochinensis Spreng) oil by nanoemulsion technique[END_REF][START_REF] Tian | Preparation and characterization of citral-loaded solid lipid nanoparticles[END_REF] poloxamer [START_REF] Badea | Use of various vegetable oils in designing photoprotective nanostructured formulations for UV protection and antioxidant activity[END_REF] and sodium taurodeoxycholate hydrate [START_REF] Salminen | Tuning of shell thickness of solid lipid particles impacts the chemical stability of encapsulated x-3 fish oil[END_REF] are example of used emulsifiers.

The use of high-speed homogenization process is often limited by the need of high energy input and the high temperature which cause oil loss.

Ultrasonication / high speed homogenization

Solid lipid nanoparticles may also be prepared by ultrasonication or high-speed homogenization technique. In brief, the heated aqueous phase was added to the melted lipid phase and emulsified by high speed stirrer, probe sonication or by adding the aqueous phase drop by drop to the lipid phase under magnetic stirring. The obtained pre-emulsion was ultrasonicated using probe sonicator with water bath (Fig. 7.c). In order to prevent recrystallization during the process, the production temperature was kept at least 5ºC above the lipid melting point [START_REF] Ramteke | Solid lipid nanoparticle : A review[END_REF][START_REF] Yadav | Solid lipid nanoparticles-A review[END_REF].

With respect to the encapsulation of plant oils, the ultrasonication technique is widely used, as described in Table 3. Zataria multiflora EO-loaded SLN were developed using Precirol ® ATO 5 (Glyceryl monostearate) as lipidic matrix and tween 80 with poloxamer 188 as surfactants [START_REF] Nasseri | Antifungal activity of Zataria multiflora essential oil-loaded solid lipid nanoparticles in-vitro condition[END_REF]. The obtained SLN owned a particle size around 255.5 nm with zeta potential of -37.8 mV and high EE% of 84 %. The same technique was used to develop cardamom EO loaded-NLC using cocoa butter (as solid lipid), olive oil (as liquid lipid) and tween 80 (as surfactant); and the resultant particles had round shape, smooth surface with particle size less than 100 nm [START_REF] Nahr | Food grade nanostructured lipid carrier for cardamom essential oil : Preparation, characterization and antimicrobial activity[END_REF]. Similarly, NLC were developed using palm stearin as solid lipid and lecithin as emulsifier and the resultant particles were physically and chemically stable during 70-day storage at room temperature and 4 °C [START_REF] Zhu | Preparation and characterization of novel nanocarriers containing krill oil for food application[END_REF].

Furthermore, [START_REF] Noor | The effect of virgin coconut oil loaded solid lipid particles (VCO-SLPs ) on skin hydration and skin elasticity[END_REF] successfully loaded coconut VO into SLN by the same process and reported high EE% (99.97%).

Like all the colloidal formulations discussed above, both SLN and NLC prepared by high-speed homogenization provide a controlled release profile of plant oils [START_REF] Pivetta | Development of nanoparticles from natural lipids for topical delivery of thymol : Investigation of its anti-inflammatory properties[END_REF][START_REF] Zhao | Solid lipid nanoparticles for sustained pulmonary delivery of Yuxingcao essential oil: Preparation, characterization and in vivo evaluation[END_REF]. The release profile of EO from these nanocarriers may be affected by several factors such as the particle size and the composition of lipidic matrix. In 2011, Garg and his coworkers compared the release profile of eugenol from SLN and NLC formulations made from stearic acid and the mixture stearic acid: caprylic triglyceride, respectively [START_REF] Garg | Enhancement in antifungal activity of eugenol in immunosuppressed rats through lipid nanocarriers[END_REF]. Results revealed a biphasic release pattern from both nanocarriers. After initial burst release, the cumulative amounts of eugenol released within 12 h were 65 and 78% from SLN and NLC, respectively. This was related to the structure of the nanocarrier's matrix. The addition of liquid lipid in the case of NLC provides fewer barriers to partitioning of eugenol to the dissolution media. The authors ascribed also this result to the small particle size of NLC (87.7 nm) as compared to that of SLN (332 nm). Indeed, the addition of liquid lipid decreases the viscosity of the organic phase (lipid solution) to be dispersed in the aqueous one resulting in smaller particles. Moreover, liquid lipid may inhibit the crystallization of solid lipid leading to smaller particle size [START_REF] Garg | Enhancement in antifungal activity of eugenol in immunosuppressed rats through lipid nanocarriers[END_REF]. One may conclude that the incorporation of liquid lipid improves the EE% but decreases the barrier provided by lipid matrix for the diffusion of bioactive molecule in the dissolution medium.

The particle size and zeta potential of NLC were influenced by several parameters including solid lipid composition, oil and surfactant (type and concentration), lipid:surfactant ratio, etc. The impact of these factors was extensively studied in the literature [START_REF] Krasodomska | Protection and viability of fruit seeds oils by nanostructured lipid carrier (NLC) nanosuspensions[END_REF][START_REF] Lacatusu | Lipid nanoparticles based on omega-3 fatty acids as effective carriers for lutein delivery . Preparation and in vitro characterization studies[END_REF][START_REF] Soleimanian | Formulation and characterization of novel nanostructured lipid carriers made from beeswax , propolis wax and pomegranate seed oil[END_REF]. It was found that increasing stearic acid concentration results in increasing the size of Eugenia caryophyllata EO-loaded SLN prepared by ultrasonication method [START_REF] Bazzaz | Solid lipid nanoparticles carrying Eugenia caryophyllata essential oil : the novel nanoparticulate systems with broad-spectrum antimicrobial activity[END_REF]. Moreover, [START_REF] Soleimanian | Formulation and characterization of novel nanostructured lipid carriers made from beeswax , propolis wax and pomegranate seed oil[END_REF] developing pomegranate seed oil-loaded NLC using two types of natural waxes: beeswax and propolis wax, investigated the influence of solid lipid composition, surfactant blend concentration and oil content on NLC physicochemical properties. Results demonstrated that increasing oil amount resulted in a decrease in particle size of beeswax NLC. This was related to the reduction of core viscosity and enhancement of fluidity which results in a decrease in particle size. The opposite behavior was observed in the case of propolis wax NLC. The particle size increases by increasing the oil content. The authors ascribed that to enhanced interfacial tension or swelling rate of the core as result of greater oil concentration. Concerning the impact of solid lipid type, [START_REF] Soleimanian | Formulation and characterization of novel nanostructured lipid carriers made from beeswax , propolis wax and pomegranate seed oil[END_REF] reported that small differences in the lipid composition (particularly, the melting point) might have considerable impact on size and quality of nano lipid carriers. Beeswax consisting of a longer series of carboxylic acid homologues, alcohols and hydrocarbons exhibits higher melting point, leading to higher viscosity of the dispersed phase which in turn results in increasing particle size (203 nm). On the other hand, propolis wax having lower proportion of components produced smaller NLC (143 nm). Regarding the zeta potential, the same authors reported that increasing the concentration of surfactant mixture (Lecithin:Tween 80) results in decreasing the zeta potential of NLC. They related this result to the differences in mobility and redistribution of used surfactants. In fact, high amounts of surfactant decrease the surface tension and enhance the particle partition during homogenization, resulting to a decrease in particle size and thus new NLC appear. The time required for the redistribution of surfactant molecules to cover the new surfaces differ. Indeed, low molecular weight surfactants such as tween 80 adsorb rapidly at the interface, while lecithin, as high molecular weight surfactant, needs more time to be adsorbed.

Therefore, tween 80, external hydrophilic non-ionic surfactant, will cover the internal lipophilic surfactant (i.e. lecithin), and thus the zeta potential decreases [START_REF] Soleimanian | Formulation and characterization of novel nanostructured lipid carriers made from beeswax , propolis wax and pomegranate seed oil[END_REF].

In summary, the ultrasonication is chosen by scientists to design both SLN and NLC systems to entrap plant oils. The commonly used lipid are glyceryl behenate [START_REF] Zhao | Solid lipid nanoparticles for sustained pulmonary delivery of Yuxingcao essential oil: Preparation, characterization and in vivo evaluation[END_REF], stearic acid [START_REF] Bazzaz | Solid lipid nanoparticles carrying Eugenia caryophyllata essential oil : the novel nanoparticulate systems with broad-spectrum antimicrobial activity[END_REF]Garg andSingh, 2013, 2011), carnauba wax [START_REF] Lacatusu | Lipid nanoparticles based on omega-3 fatty acids as effective carriers for lutein delivery . Preparation and in vitro characterization studies[END_REF], whey protein isolate [START_REF] Azizi | Study of the physicochemical properties of fish oil solid lipid nanoparticle in the presence of palmitic acid and quercetin[END_REF], glycerol stearate [START_REF] Lacatusu | Lipid nanoparticles based on omega-3 fatty acids as effective carriers for lutein delivery . Preparation and in vitro characterization studies[END_REF], palmitic acid [START_REF] Azizi | Study of the physicochemical properties of fish oil solid lipid nanoparticle in the presence of palmitic acid and quercetin[END_REF], propolis [START_REF] Soleimanian | Formulation and characterization of novel nanostructured lipid carriers made from beeswax , propolis wax and pomegranate seed oil[END_REF], palm stearin [START_REF] Zhu | Preparation and characterization of novel nanocarriers containing krill oil for food application[END_REF], beeswax [START_REF] Shakeri | Carvacrol and astaxanthin co-entrapment in beeswax solid lipid nanoparticles as an efficient nano-system with dual antioxidant and anti-biofilm activities[END_REF][START_REF] Soleimanian | Formulation and characterization of novel nanostructured lipid carriers made from beeswax , propolis wax and pomegranate seed oil[END_REF], illipe butter [START_REF] Pivetta | Development of nanoparticles from natural lipids for topical delivery of thymol : Investigation of its anti-inflammatory properties[END_REF], cocoa butter [START_REF] Nahr | Food grade nanostructured lipid carrier for cardamom essential oil : Preparation, characterization and antimicrobial activity[END_REF], Precirol® ATO 5 (glyceryl palmitostearate) [START_REF] Ghodrati | Encapsulation of Peppermint essential oil in nanostructured lipid carriers : In vitro antibacterial activity and accelerative effect on infected wound healing[END_REF], miglyol®812 (caprylic/caprictriglycerides) [START_REF] Ghodrati | Encapsulation of Peppermint essential oil in nanostructured lipid carriers : In vitro antibacterial activity and accelerative effect on infected wound healing[END_REF] and myverol® RX GMS 95P (mixture of glycerol palmitic (57,8%) stearic (37.3%) and myristic (1.3%) acid) [START_REF] Krasodomska | Protection and viability of fruit seeds oils by nanostructured lipid carrier (NLC) nanosuspensions[END_REF]. Lecithin [START_REF] Soleimanian | Formulation and characterization of novel nanostructured lipid carriers made from beeswax , propolis wax and pomegranate seed oil[END_REF][START_REF] Zhu | Preparation and characterization of novel nanocarriers containing krill oil for food application[END_REF], poly vinyl alcohol [START_REF] Zhao | Solid lipid nanoparticles for sustained pulmonary delivery of Yuxingcao essential oil: Preparation, characterization and in vivo evaluation[END_REF], tween 80 [START_REF] Lacatusu | Lipid nanoparticles based on omega-3 fatty acids as effective carriers for lutein delivery . Preparation and in vitro characterization studies[END_REF][START_REF] Nahr | Food grade nanostructured lipid carrier for cardamom essential oil : Preparation, characterization and antimicrobial activity[END_REF][START_REF] Noor | The effect of virgin coconut oil loaded solid lipid particles (VCO-SLPs ) on skin hydration and skin elasticity[END_REF], poloxamer [START_REF] Ghodrati | Encapsulation of Peppermint essential oil in nanostructured lipid carriers : In vitro antibacterial activity and accelerative effect on infected wound healing[END_REF][START_REF] Lacatusu | Lipid nanoparticles based on omega-3 fatty acids as effective carriers for lutein delivery . Preparation and in vitro characterization studies[END_REF] and pluronic® F68 [START_REF] Pivetta | Development of nanoparticles from natural lipids for topical delivery of thymol : Investigation of its anti-inflammatory properties[END_REF] are example of used emulsifiers. The main features of the ultrasonication process including 6. Application

Agriculture field

The indiscriminate use of chemicals in field as well as during postharvest poses serious problems for the environment and the human health. The excessive application of synthetic fungicides can also have other negative side effects. The appearance of resistance in the pathogen populations has been notified for many fungi [START_REF] Saharan | Synthesis of chitosan based nanoparticles and their in vitro evaluation against phytopathogenic fungi[END_REF]. In addition, over the last few years increasing consumers concern regarding contamination of crops with fungicidal residues has been reported [START_REF] Shukla | Essential oils as green pesticides for postharvest disease management[END_REF]. Therefore, low toxicity and more environmentally friendly compounds as an alternative to chemical fungicides was brought to the forefront. Among them, GRAS (generally regarded as safe) antifungal compounds such as EO have been reported [START_REF] Shukla | Essential oils as green pesticides for postharvest disease management[END_REF][START_REF] Sotelo-Boyás | Characterization of chitosan nanoparticles added with essential oils. In vitro effect on Pectobacterium carotovorum[END_REF]. Due to their broad spectrum of activity against plant pathogenic fungi and insects-pests, EO have been used as antifungal, insecticidal, repellent, antifeedant and oviposition deterrent [START_REF] De Souza | Inhibitory action of some essential oils and phytochemicals on the growth of various moulds isolated from foods[END_REF][START_REF] Shukla | Essential oils as green pesticides for postharvest disease management[END_REF]. However, the replacement of synthetic compounds is not easy due to the poor stability shown by EOs during the processing steps. Therefore, nanoencapsulation has been proposed for this purpose [START_REF] Maryam | Nanoencapsulation of essential oils with enhanced antimicrobial activity : A new way of combating antimicrobial Resistance[END_REF]. According to the literature, pNPs are widely used for EO encapsulation in agriculture industry.

Recently, [START_REF] Khoobdel | Insecticidal activity of polycaprolactone nanocapsules loaded with Rosmarinus officinalis essential oil in Tribolium castaneum (Herbst)[END_REF] investigated the insecticidal activity of Rosmarinus officinalis EO-loaded pNPs against the red flour beetle, Tribolium castaneum. Fumigant and contact toxicity assays revealed that the developed particles had significant increase in fumigant and contact toxicity as compared to the pure EO. At the 72 h exposure for fumigant toxicity, the mortality of Tribolium castaneum adults was 83.3 % for free EO at a concentration of 27.76 μL/L air and 100 % for EO-loaded nanoparticles at concentration of 19.12 μL/L air [START_REF] Khoobdel | Insecticidal activity of polycaprolactone nanocapsules loaded with Rosmarinus officinalis essential oil in Tribolium castaneum (Herbst)[END_REF]. Moreover, [START_REF] Zhaveh | Encapsulation of Cuminum cyminum essential oils in chitosancaffeic acid nanogel with enhanced antimicrobial activity against Aspergillus flavus[END_REF] related the superior performance of Cuminum cyminum EO nanogels against Aspergillus flavus as compared to the free oil to the encapsulation in chitosan : cafeic acid nanoparticles. Similar results were already reported when investigating insecticidal activity against Bemisia tabaci for Zanthoxylum rhoifolium EO-loaded nanoparticles as compared to the free oil [START_REF] Christofoli | Insecticidal effect of nanoencapsulated essential oils from Zanthoxylum rhoifolium (Rutaceae) in Bemisia tabaci populations[END_REF]. Therefore, the nanoencapsulation can enhance the insecticidal potential of EO due to the controlled and slow release of EO and increased surface area of the nanoparticles.

Sotelo-Boyas and his coworkers (2015) combined the bacterial efficiency of chitosan with those of lime and thyme EO in pNPs to eradicate Pectobacterium carotovorum, plant phytopathogenic bacteria, involved in the decay of fresh vegetables and fruits like radishes, onions, potatoes, cucumbers, carrots, eggplant, squash, peppers, tomato and cabbage. For instance, chitosan was highly used for its potential effect in the control of phytopathogenic fungi Gram-negative and Gram positive bacteria [START_REF] Benhabiles | Antibacterial activity of chitin, chitosan and its oligomers prepared from shrimp shell waste[END_REF][START_REF] Kaur | An in vitro study of the antifungal activity of silver/chitosan nanoformulations against important seed borne pathogens[END_REF][START_REF] Zhu | Enhanced water-solubility and antibacterial activity of novel chitosan derivatives modified with quaternary phosphonium salt[END_REF]. The antibacterial study demonstrated that thyme based-nanoparticles showed the highest inhibitory effect on the growth of Pectobacterium carotovorum than free chitosan nanoparticles and lime based-nanoparticles. The inhibition halo diameters were found 15, 13 and 24 mm for chitosan free nanoparticles, lime-chitosan nanoparticles and Thyme-chitosan nanoparticles, respectively. Moreover, the number of colonies forming units (CFU) could not be determined (countless colonies) for chitosan free nanoparticles. While for lime-and thymechitosan nanoparticles, CFU were found 450 and 240, respectively [START_REF] Sotelo-Boyás | Characterization of chitosan nanoparticles added with essential oils. In vitro effect on Pectobacterium carotovorum[END_REF].

Furthermore, the results of antifungal assay carried out on chitosan:pepper tree EO nanoparticles revealed that higher activity was assessed for the nanoparticles on the viability of Aspergillus parasiticus spores as compared to that of chitosan and pepper tree oil present individually. One may conclude that the antifungal effect of chitosan nanoparticles was attributed to two reasons: 1) the small size of nanoparticles will increase the contact area with fungus;

2) The cationic nature of chitosan allows electrostatic interaction with proteins and phospholipids of the plasmatic membrane of the microorganism which in turn cause membrane destabilization and death.

With respect to the use of lipid based-nanocarriers in agriculture industry, few reports have been investigated in the last decade. Liposomes were used for the first time for rosemary EO encapsulation to inhibit the seed germination of invasive alien species (Acacia saligna) [START_REF] Maccioni | Inhibitory effect of rosemary essential oil, loaded in liposomes, on seed germination of Acacia saligna (Labill.) Wendl., an invasive species in Mediterranean ecosystems[END_REF]. The incorporation of rosemary EO in liposomes limited the loss of EO volatile components and delivering them into the seed resulting in enhancing EO efficacy.

Similarly, [START_REF] Adel | Biological activity and field persistence of Pelargonium graveolens (Geraniales : Geraniaceae) loaded solid lipid nanoparticles (SLNs) on Phthorimaea operculella (Zeller) (PTM) (Lepidoptera : Gelechiidae)[END_REF] pointed out that Pelargonium graveolens EO loaded-SLN were stable under field conditions and exhibit higher larvicidal activity against Phthorimaea operaculella as compared to the free oil.

Food field

In recent years, consumer demands in eating healthy and less processed foods have boosted remarkably. Functional foods play a pivotal role in promoting health and preventing degenerative diseases such as heart disease, cancer and diabetes, which account for almost two thirds of deaths in the world [START_REF] Conto | Effects of the addition of microencapsulated omega-3 and rosemary extract on the technological and sensory quality of white pan bread[END_REF][START_REF] Rubilar | Development of a soup powder enriched with microencapsulated linseed oil as a source of omega-3 fatty acids[END_REF]. Foods enriched with long chain omega-3 polyunsaturated fatty acids are classified as functional foods by acting on human health. The ingestion of omega-3 fatty acids is accompanied with a prevention of cardiovascular diseases, a decreased risk of cancer, autoimmune and inflammatory diseases [START_REF] Azizi | Study of the physicochemical properties of fish oil solid lipid nanoparticle in the presence of palmitic acid and quercetin[END_REF][START_REF] Conto | Effects of the addition of microencapsulated omega-3 and rosemary extract on the technological and sensory quality of white pan bread[END_REF][START_REF] Gallardo | Microencapsulation of linseed oil by spray drying for functional food application[END_REF]. However, polyunsaturated fatty acids are very susceptible to oxidation during processing and storage resulting in decreased nutritional value and sensory quality. Thus, micro and nanoencapsulation of lipids have been used in this concern [START_REF] Gökmen | Development of functional bread containing nanoencapsulated omega-3 fatty acids[END_REF].

Currently, several nanocarriers have been designed in the literature to encapsulate several healthful oils like chia seed oil [START_REF] Campo | Nanoencapsulation of chia seed oil with chia mucilage (Salvia hispanica L.) as wall material: characterization and stability evaluation[END_REF], walnut oil [START_REF] Shamaei | Microencapsulation of walnut oil by spray drying : Effects of wall material and drying conditions on physicochemical properties of microcapsules[END_REF], flaxseed oil [START_REF] Carneiro | Encapsulation efficiency and oxidative stability of flaxseed oil microencapsulated by spray drying using different combinations of wall materials[END_REF][START_REF] Gallardo | Microencapsulation of linseed oil by spray drying for functional food application[END_REF][START_REF] Pu | Developing microencapsulated flaxseed oil containing shrimp (Litopenaeus setiferus) astaxanthin using a pilot scale spray[END_REF], pomegranate oil [START_REF] Soleimanian | Formulation and characterization of novel nanostructured lipid carriers made from beeswax , propolis wax and pomegranate seed oil[END_REF], roasted coffee oil [START_REF] Freiberger | Encapsulation of roasted coffee oil in biocompatible nanoparticles[END_REF] and fruit seed oil (blackcurrant, blackberry, raspberry, strawberry and plum) [START_REF] Krasodomska | Protection and viability of fruit seeds oils by nanostructured lipid carrier (NLC) nanosuspensions[END_REF]. In 2012, Rubilar et al. developed a soup fortified with linseed oil microcapsules and depicted that microencapsulation protected linseed oil from oxidation with respect to free oil [START_REF] Rubilar | Development of a soup powder enriched with microencapsulated linseed oil as a source of omega-3 fatty acids[END_REF]. Similarly, [START_REF] Gökmen | Development of functional bread containing nanoencapsulated omega-3 fatty acids[END_REF] demonstrated the feasibility to include flaxseed oil nanoparticles in bread without affecting the sensorial properties.

At the same time, foods are paramount carriers of many damaging agents like virus, bacteria, parasites, and toxins which can cause food-borne diseases [START_REF] Dussault | In vitro evaluation of antimicrobial activities of various commercial essential oils, oleoresin and pure compounds against food pathogens and application in ham[END_REF].

Every year, around 30% of people suffer from foodborne diseases in developed countries [START_REF] Lee | Antibacterial mechanism of Myagropsis myagroides extract on Listeria monocytogenes[END_REF]. Meanwhile, due to the increased consumer awareness to the use of synthetic food preservatives or aromatic agents, the tendency toward natural ones is gaining more and more attention [START_REF] Alikhani-Koupaei | Liposomal and edible coating as control release delivery systems for essential oils : comparison of application on storage life of fresh-cut banana[END_REF]. In light of that, using EO with antioxidant, antibacterial and antifungal properties and applying nanoparticulate systems are effective approaches in this regard [START_REF] Bazzaz | Solid lipid nanoparticles carrying Eugenia caryophyllata essential oil : the novel nanoparticulate systems with broad-spectrum antimicrobial activity[END_REF][START_REF] Khatibi | Effect of nanoliposomes containing Zataria multiflora Boiss . essential oil on gene expression of Shiga toxin 2 in Escherichia coli O157 : H7[END_REF]. In 2017, Cui and his coworkers developed thyme EO-loaded liposomes to treat salmonellosis, an important food-borne disease, usually associated with direct consumption or cross contamination of animal origin foods, especially poultry, and poultry related products (Cui et al., 2017b). They investigated in their study the time-kill analysis of liposome-encapsulated thyme oil on fresh chicken contaminated with Salmonella enteritidis. Results demonstrated that Salmonella enteritidis colonies reduced by 71.16, 90.45, 83.02, 89.53 and 97.71% after exposure to 300 mg/mL liposomes for 3, 4, 5, 6, and 7 days, respectively (Cui et al., 2017b). In another work study, the antimicrobial activity of curry plant EO loaded-liposomes against Bacillus cereus in rice flour was investigated (Cui et al., 2017a). Results showed that the antibacterial activity and active time of curry plant EO loaded-liposomes were significantly boosted when compared to the free EO. For instance, the population of Bacillus cereus in rice flour was almost unchanged or even increased after EO treatment. However, it reduced significantly after 4 days liposomes treatment (Cui et al., 2017a). Gomes et al. (2011b) related the boosting in trans cinnamaldehyde or -eugenol against both Salmonella and Listeria Spp activity to three reasons: the improved hydrophilicity, the sustained release, and the small size of pNPs. In 2018, Lin et al. investigated the antimicrobial activity of thyme EO-loaded liposomes against Escherichia coli O157:H7 in four vegetable juices: tomato, carrot, cucumber and lettuce juices [START_REF] Lin | Improving the stability of thyme essential oil solid liposome by using β -cyclodextrin as a cryoprotectant[END_REF]. Indeed, Enterohaemorrhagic Escherichia coli serotype O157:H7 as a main human pathogen may cause food borne outbreaks, bloody diarrhea, hemorrhagic colitis and hemolytic uremic syndrome and even death [START_REF] Khatibi | Effect of nanoliposomes containing Zataria multiflora Boiss . essential oil on gene expression of Shiga toxin 2 in Escherichia coli O157 : H7[END_REF]. Results showed that solid liposomes exhibited significant reduction in Escherichia coli O157:H7 when compared to group control. For instance, no bacterial growth was observed on nutrient agar plate in the case of cucumber juice and lettuce juice treated with 5 mg/mL liposomes. While, treating tomato juice and carrot juice with the same concentration of liposomes lead to 99.99 and 99.80% reduction of Escherichia coli O157:H7 [START_REF] Lin | Improving the stability of thyme essential oil solid liposome by using β -cyclodextrin as a cryoprotectant[END_REF]. Moreover, [START_REF] Khatibi | Effect of nanoliposomes containing Zataria multiflora Boiss . essential oil on gene expression of Shiga toxin 2 in Escherichia coli O157 : H7[END_REF] found that the relative transcriptional level of Stx2A gene of Escherichia coli O157:H7 was decreased from 0.721 to 0.646 when using 75% minimum inhibitory concentration (MIC) of Zataria multiflora EO loaded-nanoliposomes.

The antibacterial mechanism of EOs loaded-nanocarriers has been investigated. In 2015,

Cui et al. investigated the antibacterial mechanism of liposomes containing clove EO against

Staphylococcus aureus in Tofu [START_REF] Cui | The specific antibacterial activity of liposome-encapsulated clove oil and its application in tofu[END_REF]. A selective antimicrobial activity for Staphylococcus aureus by means of pore-forming toxins to activate clove oil release from liposomes was noticed. In fact, the liposomes did not fuse with biological membranes but release clove oil after toxins secretion by the bacteria. About 99.87% reduction in population was observed in Staphylococcus aureus after 24 h of liposome treatment. However, no reduction was observed in Escherichia coli population after liposome treatment due to the fact that these bacteria did not secrete toxins and therefore clove oil could not reach them [START_REF] Cui | The specific antibacterial activity of liposome-encapsulated clove oil and its application in tofu[END_REF].

The antioxidant and antimicrobial activities of EO-loaded nanocarriers were found to be conserved for long period. In this context, the physicochemical qualities of fresh-cut bananas in contact with free rosemary EO, rosemary oil plus mucilage and rosemary oil liposomes were evaluated during 9 days storage at 5°C (Alikhani-Koupaei, 2015). Sensory analysis revealed that liposomal formulations was more efficient in enhancing the quality of fresh-cut bananas and extending their shelf life [START_REF] Alikhani-Koupaei | Liposomal and edible coating as control release delivery systems for essential oils : comparison of application on storage life of fresh-cut banana[END_REF]. Likewise, the conversion of cardamom EO to NLC [START_REF] Nahr | Food grade nanostructured lipid carrier for cardamom essential oil : Preparation, characterization and antimicrobial activity[END_REF] and nanoliposomes [START_REF] Nahr | Investigation of physicochemical properties of essential oil loaded nanoliposome for enrichment purposes[END_REF] greatly conserves its antioxidant and antimicrobial activities for long period. The NLC showed MIC values around 1100 µg/ml for both bacteria after 30 days compared to that of cardamom oil emulsion. The MIC values were around 4400 and 2200 µg/ml for Staphylococcus aureus and Escherichia coli, respectively [START_REF] Nahr | Food grade nanostructured lipid carrier for cardamom essential oil : Preparation, characterization and antimicrobial activity[END_REF].

The biological activity of nanocarriers encapsulated plant oils was affected by operating parameters and particles ingredients. In 2017, Mohammed and his coworkers depicted that a high antioxidant efficiency of Nigella sativa EO-loaded microparticles prepared by spray drying process was associated with high ratio of wall material (30%), medium of oil concentration (10%) and low inlet temperature (160°C) [START_REF] Mohammed | Process conditions of spray drying microencapsulation of Nigella sativa oil[END_REF]. those containing stearic acid compared to glycerol monostearate [START_REF] Bazzaz | Solid lipid nanoparticles carrying Eugenia caryophyllata essential oil : the novel nanoparticulate systems with broad-spectrum antimicrobial activity[END_REF].

In recent years, the use of EO has emerged to the food packaging industry as reported by several work studies (Cui et al., 2016a(Cui et al., , 2016b;;[START_REF] Engel | Antimicrobial activity of free and liposome-encapsulated thymol and carvacrol against Salmonella and Staphylococcus aureus adhered to stainless steel[END_REF][START_REF] Liu | Development of poly (lactic acid)/ chitosan fibers loaded with essential oil for antimicrobial applications[END_REF]. Cinnamon EO, known for its antimicrobial properties, has been formulated in chitosan/poly lactic acid fibers for food packaging application as an alternative for synthetic chemicals due to consumer concerns over food safety [START_REF] Liu | Development of poly (lactic acid)/ chitosan fibers loaded with essential oil for antimicrobial applications[END_REF]. Results showed high long-term inactivation rates against Escherichia coli and Staphylococcus aureus [START_REF] Liu | Development of poly (lactic acid)/ chitosan fibers loaded with essential oil for antimicrobial applications[END_REF]. Cinnamon EO was further formulated in liposomes and tested for its Methicillin-resistant Staphylococcus aureus antibiofilm properties on the surfaces of different materials like stainless steel, gauze, nylon membrane, and non-woven fabrics (Cui et al., 2016a). Results revealed a significant enhancement of the anti-biofilm activities and active time for liposome-encapsulated cinnamon EO when compared to the free oil. For instance, the counts of viable Staphylococcus aureus in biofilms formed were reduced by 2.08 and 2.82 logs on gauze and 4.55 and 5.42 logs on nonwoven fabrics after five days treatment with free cinnamon oil and liposome containing cinnamon oil, respectively (Cui et al., 2016a). Additionally, the antibacterial effect of salvia EO nanoliposomes against Staphylococcus aureus biofilms attached on milk container was explored by scanning electron microscopy and confocal laser scanning microscopy and results revealed that salvia EO nanoliposomes have high anti-biofilm activity against Staphylococcus aureus biofilms on milk container (Cui et al., 2016b). Furthermore, [START_REF] Engel | Antimicrobial activity of free and liposome-encapsulated thymol and carvacrol against Salmonella and Staphylococcus aureus adhered to stainless steel[END_REF] noticed the antimicrobial potential of liposome-encapsulated thymol and carvacrol against pools of Staphylococcus aureus and Salmonella adhered to stainless steel.

Medicinal field

Antimicrobial activity

The management of bacterial infection is raising serious concern across the globe. The emergence of multi-drug-resistant bacterial pathogens and the ability of microorganisms to form biofilms result high tolerance to high amounts of antibiotics and to all host defense mechanisms [START_REF] Mandal | Challenges and future prospects of antibiotic therapy: from peptides to phages utilization[END_REF]. Faced with this challenge, the scientists throughout the world search for new antimicrobial agents, such as plant oils based formulations which are economic and ecologic antimicrobial agents; and combine them with nanotechnology [START_REF] Liakos | Cellulose acetate -essential oil nanocapsules with antimicrobial activity for biomedical applications[END_REF]. In this context, Ianniteli et al. ( 2011) investigated the effects of carvacrol-loaded poly (lactide-co-glycolide)-nanocapsules on the viscoelastic features of Staphylococcus epidermidis biofilms by rheological measurements. Results revealed the ability of carvacrol loaded nanoparticles to reduce the elasticity and mechanical stability of preformed biofilms which in turn enable the penetration of antimicrobial agents into the deep core of biofilms [START_REF] Iannitelli | Potential antibacterial activity of carvacrol-loaded poly(DL-lactide-co-glycolide) (PLGA) nanoparticles against microbial biofilm[END_REF]. [START_REF] Liakos | Polylactic acid-lemongrass essential oil nanocapsules with antimicrobial properties[END_REF] tested the antibiofilm activity of poly lactide nanoparticles encapsulating lemongrass EO against Candida albicans, Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. Results showed higher anti-biofilm effect for Candida albicans and Escherichia coli tested strains. The cytotoxicity of the prepared nanoparticles was further analyzed and results revealed a high cell viability and good growth of human cells [START_REF] Liakos | Polylactic acid-lemongrass essential oil nanocapsules with antimicrobial properties[END_REF]. Subsequently, in 2018, the same research team tested the antibiofilm activity of cellulose acetate pNPs containing either lemongrass, peppermint or cinnamon EO and the results showed high antibiofilm activity against Candida albicans and Staphylococcus aureus [START_REF] Liakos | Cellulose acetate -essential oil nanocapsules with antimicrobial activity for biomedical applications[END_REF]. [START_REF] Manconi | Thymus essential oil extraction, characterization and incorporation in phospholipid vesicles for the antioxidant / antibacterial treatment of oral cavity diseases[END_REF]proposed the use of liposomes containing Thymus capitatus EO as antibacterial-antioxidant mouthwash for the treatment of oral cavity diseases. The liposomes were biocompatible, able to prevent oxidative stress and favor wound repair in keratinocytes. Their antibacterial activity was evidenced against commensal Streptococcus sanguinis and cariogenic Streptococcus mutans and Lactobacillus acidophilus [START_REF] Manconi | Thymus essential oil extraction, characterization and incorporation in phospholipid vesicles for the antioxidant / antibacterial treatment of oral cavity diseases[END_REF]. Similarly, [START_REF] Priyadarshini | Formulation and characterisation of poly ( lactic-co-glycolic acid ) encapsulated clove oil nanoparticles for dental applications[END_REF] proposed the use of poly (lactide-co-glycolide)-nanoparticles containing clove EO as antibacterial systems for dental purposes by removing bacterial plaque and reducing dental diseases. Confocal microscopy demonstrated successful delivery and position of clove oil loaded-nanoparticles inside dentinal tubules. In another work study, the antiviral activity of Santolina insularis EO loaded-liposomes against Herpes simplex virus-type 1 was investigated [START_REF] Valenti | Liposome-incorporated Santolina insularis essential oil: Preparation, characterization and in vitro antiviral activity[END_REF]. Although the in vitro activity of free oil was higher than liposomal oil, the high stability of liposomes make them an interesting delivery system for antiviral treatment;

they could be administered in drops for ocular herpetic infection, parenterally for diffused systemic infections or topically on lips and mucosae from gel or cream formulations [START_REF] Valenti | Liposome-incorporated Santolina insularis essential oil: Preparation, characterization and in vitro antiviral activity[END_REF]. Furthermore, [START_REF] Zhao | Solid lipid nanoparticles for sustained pulmonary delivery of Yuxingcao essential oil: Preparation, characterization and in vivo evaluation[END_REF] highlighted the use of SLN as a carrier for the encapsulation and sustained inhalation delivery of yuxingcago EO for the treatment of respiratory infectious diseases. Besides prolonging pulmonary retention up to 24h after intratracheal administration to rats, yuxingcago EO loaded-SLN enhance the area under the curve (AUC ) values by 4.5-7.7 folds compared to the intratracheally dosed EO solution and by 257-438 folds to the intravenously dosed EO solution [START_REF] Zhao | Solid lipid nanoparticles for sustained pulmonary delivery of Yuxingcao essential oil: Preparation, characterization and in vivo evaluation[END_REF].

Antifungal activity

Considering the antifungal properties of Zataria multiflora EO, Nasseri et al. developed Zataria multiflora EO loaded-SLN to enhance its activity against Aspergillus ochraceus, Aspergillus niger, Aspergillus flavus, Alternaria solani, Rhizoctonia solani, and Rhizopus stolonifera [START_REF] Nasseri | Antifungal activity of Zataria multiflora essential oil-loaded solid lipid nanoparticles in-vitro condition[END_REF]. Results showed that the encapsulated oil was more efficient than the free one. For instance, the MIC for the encapsulated oil on the fungal pathogens of and viability, delayed mycelial growth and reduced aflatoxin production.

Larvicidal activity

Currently, several reports has demonstrated the larvicidal activity of Lippia sidoides EO against larvae of Aedes (Stegomyia aegypti), the dengue vector which is responsible for many diseases, and even deaths, in tropical countries like Brazil [START_REF] Carvalho | Larvicidal activity of the essential oil from Lippia sidoides Cham. against Aedes aegypti Linn[END_REF]. In order to boost its larvicidal effect,

Antitumor activity

The antitumor activity of frankincense and myrrh oil loaded-SLN was assessed on H22

tumor-bearing mice and results revealed an enhancement in antitumor efficiency of SLN when compared to that of suspension and cyclodextrine inclusion [START_REF] Wang | Preparation and characterization of solid lipid nanoparticles loaded with frankincense and myrrh oil[END_REF]. The inhibition rates were 31.23, 34.81 and 43.66% for oil suspension, oil-β-cyclodextrin and oil-SLN, respectively.

Similarly, [START_REF] Celia | Anticancer activity of liposomal bergamot essential oil (BEO) on human neuroblastoma cells[END_REF] found that liposomal formulations encapsulating bergamot EO showed a greater reduction in human SH-SY5Y neuroblastoma cells viability and a greater increase in cell mortality at various concentrations and time points as compared to their free drug counterparts. Same results were also reported by [START_REF] Detoni | Evaluation of thermal-oxidative stability and antiglioma activity of Zanthoxylum tingoassuiba essential oil entrapped into multi-and unilamellar liposomes[END_REF] where MLVs and SUVs containing Zanthoxylum tingoassuiba EO were more efficient in reducing the viability of glioma cells than free EO. In another work study, docosahexaenoic acid was encapsulated in liposomes and investigated for its anticancer activity and results showed a strong inhibition of FaDu head, neck squamous carcinoma and 4T1 breast cancer cells in in vitro cultures [START_REF] Alaarg | Docosahexaenoic acid liposomes for targeting chronic inflammatory diseases and cancer : an in vitro assessment[END_REF]. In 2013, Shi and his coworkers developed NLC containing β-elemene and investigated their pharmacokinetics, anti-tumor effects, and venous irritation [START_REF] Shi | Formulation design, preparation, and in vitro and in vivo characterizations of β -elemene-loaded nanostructured lipid carriers[END_REF].

In this study, β-elemene-NLC suspensions were injected in an ear vein test, and compared with elemene injection and saline solution used as positive and negative controls, respectively.

Results demonstrated no obvious discoloration or damage at the injection site in either βelemene-NLC groups or saline solution group, two days after the injection. However, unencapsulated β-elemene caused macroscopic edema and erythema at the injection site.

Additionally, the pharmacokinetic study revealed that the availability of the β-elemene was increased by formulation into NLC since they showed higher AUC and slower clearance as compared to elemene injection. Furthermore, the anti-tumor efficacy of β-elemene-NLC was significantly higher than that of elemene injections with inhibition rates of 34.36 and 24.11%, respectively [START_REF] Shi | Formulation design, preparation, and in vitro and in vivo characterizations of β -elemene-loaded nanostructured lipid carriers[END_REF].

Cosmetic field

Wound healing is one of the most complicated physiological processes. Indeed, tissue regeneration enhancement and infection prevention are key factors to reduce pain, discomfort, and scar formation [START_REF] Jahromi | Nanomedicine and advanced technologies for burns: preventing infection and facilitating wound healing[END_REF]. Several chemical products have been proposed for wound repair; however, their uses are limited due to the complications and side effects [START_REF] Purohit | Experimental evaluation of Aloe vera leaves pulp as topical medicament on wound healing[END_REF]. Recently, researchers have paid great attention to the effectiveness of plant oils thanks to their antioxidant, antimicrobial, and anti-inflammatory properties [START_REF] Raut | Experimental evaluation of Aloe vera leaves pulp as topical medicament on wound healing[END_REF]. In this context, [START_REF] Ghodrati | Encapsulation of Peppermint essential oil in nanostructured lipid carriers : In vitro antibacterial activity and accelerative effect on infected wound healing[END_REF] healing in rat burn model by cell proliferation enhancement, good bioadhesion, cell biocompatibility and antimicrobial properties [START_REF] Saporito | Essential oil-loaded lipid nanoparticles for wound healing[END_REF]. In 2018, Pivetta et al.

prepared carbopol-gels containing thymol loaded-NLC as promising approach for treating skin inflammatory disorders [START_REF] Pivetta | Development of nanoparticles from natural lipids for topical delivery of thymol : Investigation of its anti-inflammatory properties[END_REF]. In their study, they investigated the antiinflammatory effects of thymol-NLC gel on two mouse models: the cutaneous acute inflammation model induced by croton oil and ear edema model induced by anthralin. Results

showed that thymol encapsulated in NLC provided better anti-inflammatory effect than free thymol [START_REF] Pivetta | Development of nanoparticles from natural lipids for topical delivery of thymol : Investigation of its anti-inflammatory properties[END_REF].

Chronic skin infections in immunocompromised patients has become an important public health issue because they can become serious, resulting in invasive infections [START_REF] Svetlichny | Solid lipid nanoparticles containing copaiba oil and allantoin : development and role of nanoencapsulation on the antifungal activity[END_REF]. In this context, [START_REF] Ortan | Topical delivery system of liposomally encapsulated volatile oil of Anethum Graveolens[END_REF] developed hydrogels containing Anethum graveolens oil entrapped in liposomes to treat fungal infections in skin. The in vitro release kinetics study using Franz diffusion cell showed that the designed hydrogels follow a zero order kinetic model after a period of three hours from the beginning of the experiment [START_REF] Ortan | Topical delivery system of liposomally encapsulated volatile oil of Anethum Graveolens[END_REF]. Moreover, hydrogel containing eugenol entrapped in either stearic acid-or compritol-SLN were designed for epidermal targeting to treat fungal infections in skin [START_REF] Garg | Targeting of eugenol-loaded solid lipid nanoparticles to the epidermal layer of human skin[END_REF]. Ex vivo permeation and retention studies for almond oil solution of eugenol and three types of hydrogels containing: eugenol-stearic acid-SLN, eugenol-compritol-SLN or eugenol-hydroxypropyl-β-cyclodextrin complex; were established with full thickness human cadaver skin using Franz diffusion cell. Results revealed higher accumulation of eugenol in the epidermis (62.65 and 52.86 μg/cm 2 for eugenol-stearic acid-SLN and eugenol-compritol-SLN, respectively) when compared to that of almond oil solution of eugenol (3.45 μg/cm 2 ) and eugenol-hydroxypropyl-β-cyclodextrine complex (9.77 μg/cm 2 ) [START_REF] Garg | Targeting of eugenol-loaded solid lipid nanoparticles to the epidermal layer of human skin[END_REF].

Currently, VO exhibit a great concern as raw materials in the development of natural and eco-friendly cosmetics due to their benefits including antioxidant, moisturizers and emollients properties. In addition, they provide skin protection against reactive oxygen species and prevent oxidative stress [START_REF] Dhavamani | Total antioxidant activity of selected vegetable oils and their influence on total antioxidant values in vivo[END_REF][START_REF] Saraf | Comparative measurement of hydration effects of herbal moisturizers[END_REF]. In order to obtain efficient formulations with UV protection performance and antioxidant activity, [START_REF] Badea | Use of various vegetable oils in designing photoprotective nanostructured formulations for UV protection and antioxidant activity[END_REF] formulated creams containing NLC entrapping various VO and their combinations (pomegranate seed oil, wheat germ oil, blackcurrant seed oil, sesame seed oil, carrot root oil, raspberry seed oil and rice bran oil) with a synthetic UVA filter (diethylamino hydroxy benzoyl hexyl benzoate). The UV protection factors were evaluated on the individual VO and on cream formulations based on NLC and results showed that the best UV protection was assured by pomegranate seed oil combined with wheat germ-loaded NLC based cream resulting in a SPF of 5.1 and an UVAPF of 9.5 [START_REF] Badea | Use of various vegetable oils in designing photoprotective nanostructured formulations for UV protection and antioxidant activity[END_REF].

Textiles

Nowadays, functional textiles fascinated consumers interest due to their crucial benefits as they enhance the native properties and promote new functions in the textile products like flame retardency, UV resistance, photo-catalytic, antimicrobial, antibiotic and wrinkle recovery to the fabrics [START_REF] Javid | Chitosan microencapsulation of various essential oils to enhance the functional properties of cotton fabric chitosan microencapsulation of various essential oils to enhance the functional properties of cotton fabric[END_REF]. In medical field, textile consumers are becoming more aware and conscious of the deleterious effect that microorganisms may have upon textile materials like drapes, bed sheets, pillow cases, gowns and masks which are frequently used in hospitals [START_REF] Thelagavath | Dual antimicrobial and blood repellent finishes for cotton hospital fabrics[END_REF]. In this context, Li et al. (2013) grafted moxa oil microcapsules made with gelatin and arabic gum on cotton fabric and investigated their antibacterial activity against Staphylococcus aureus and the results showed strong antibacterial effect. Similarly, ozonated red pepper seed oil antimicrobial microcapsules were applied on 100% polypropylene non-woven fabric and showed good antimicrobial activity against

Staphylococcus aureus, Escherichia coli and Candida albicans [START_REF] Ozyıldız | Micro-encapsulation of ozonated red pepper seed oil with antimicrobial activity and application to nonwoven fabric[END_REF].

Furthermore, [START_REF] Rajendran | Development of antimicrobial cotton fabrics using herb loaded nanoparticles[END_REF] reported that Ocimum sanctum oil loaded alginatenanoparticles possessed remarkable antibacterial activities with excellent wash durability. After 20 washes, the inhibition percentage was 100% for Bacillus cereus, Pseudomonas aeruginosa and Staphylococcus aureus except for Escherichia coli (90%). After 30 washes, the bacterial inhibition was reduced to 95, 87, 98 and 98% for Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus, respectively [START_REF] Rajendran | Development of antimicrobial cotton fabrics using herb loaded nanoparticles[END_REF]. In 2013, Javid et al. reported that antibacterial activity of cotton fabric grafted with chitosan capsules containing eucalyptus and sandal wood oils increased with the increase in chitosan and EO concentrations [START_REF] Javid | Chitosan microencapsulation of various essential oils to enhance the functional properties of cotton fabric chitosan microencapsulation of various essential oils to enhance the functional properties of cotton fabric[END_REF].

Recent developments in textile industry were conducted to perfumed textiles in jackets, sweaters, T-shirts and undershirts to meet consumers' needs for comfort and wellbeing. During wearing, the mechanical forces on the capsules result in opening of the capsules and releasing of the designed aroma and deodorant [START_REF] Ghayempour | Micro/nanoencapsulation of essential oils and fragrances: Focus on perfumed, antimicrobial, mosquito-repellent and medical textiles[END_REF]. In this context, [START_REF] Liu | Preparation and characteristics of nanocapsules containing essential oil for textile application[END_REF] treated methyl methacrylate-styrene nanoparticles containing cologne EO on the cotton fabric through immersion and the release study revealed that 6.8% cologne EO remained in fabrics after being washed 15 times. In another work, Wang et al. reported that ethyl cellulose microcapsule can retain 50% of the lavender oil after 2 months, while almost no EO persisted on the direct sprayed fabric after 7 days [START_REF] Wang | Preparation and characterization of natural fragrant microcapsules[END_REF]. Additionally, Li et al. (2013) found that orange oil retention of microcapsules on the cotton and polyester fabrics was 8 days longer than free oil.

Conclusion and perspectives

In the last two decades, the growing demand for natural bioactive products especially essential and vegetable oils with the same efficiency or even more than chemical synthesized drugs has urged researchers to focalize most of their efforts on developing new approaches of extending the shelf life of these bioactive agents. In fact, plant oils are very sensitive to external factors when used as such. The encapsulation of these bioactive agents represents a relevant alternative to extend their physical stabilities, protecting them from oxidation and other deleterious environmental factors like light, heat, oxygen and humidity, besides improving their efficacy mainly owning to their nanometer size range. In this bibliographic paper, we emphasize recent advances of both polymer and lipid based-nanocarriers including polymeric nanoparticles, liposomes and solid lipid nanoparticles in the emergence of new concepts for the effective use of plant oils. A number of benefits and drawbacks are linked to each carrier. For instance, both solid lipid nanoparticles and polymeric nanoparticles have more oil stability and prolonged release than liposomes; while liposomes offer wide application spectrum especially to the skin delivery thanks to their chemical nature which is very close to that of the skin layers.

Although solid lipid nanoparticles are safer than polymeric nanoparticles since the avoidance of organic solvents, they were less used to encapsulate both essential and vegetable oils, according to the investigations discussed above. This was may be related to the high temperature requirements which in turn cause oil loss and thus decrease the encapsulation efficiency. Several preparation methods have been reported for each nanocarrier; they are differentiated by the complexity of their execution and the characteristic of their final product; nonetheless, the right selection of the suitable carrier with the appropriate preparation method is the crucial key to determine the carrier features responsible for the best attainment of the final goal. The discussed nanostructured systems provide pertinent perspectives for applications in several fields like medicinal, cosmetic, culinary, agriculture and textiles. Nowadays, the association of plants oils and active molecules is attracting special attention. Lipid core nanocapsules and nanostructured lipid carriers represent promising carriers to entrap both plant oil and synthetic drugs. The appropriate selection of plant oil is very important for achieving the high loading capacity and physical stability of the hydrophobic drugs. In addition, the oil may complement or even enhance the biological activities of these drugs. Hence, the research in the field of plants oils encapsulation can make an important contribution to the development of new methodologies in the treatment and diagnosis of major chronic diseases.

Experimental advances are necessary in engineering plant oils loaded nanocarriers with broader applications and functionalities. Some techniques discussed in this review provide poor control over the final structure and stability of the obtained colloidal systems. Others lack from scalability and reproducibility; therefore, new techniques with improved control and reproducibility are crucial to design nanocarriers with predictable properties.

Even if several advances have been already reported in the literature regarding the application of plants oils nanocarriers for pharmaceutical and cosmetics purposes, more in vivo studies are required to provide reliable results. Additionally, plant oils mechanism of action, toxic effects, pharmacokinetic parameters, biodistribution in biological systems and removal mechanisms must be investigated. Moreover, with the aim of improving the biodistribution of colloidal systems, scientists throughout the world are currently focalizing their efforts on the

Fig. 1 .

 1 Fig. 1. Triglycerides composition of different vegetable oils.

Fig. 2 .

 2 Fig. 2. Minor components of vegetable oils.

Fig. 3 .

 3 Fig. 3. Composition of terpenes.

Fig. 4 .

 4 Fig. 4. Examples of phenylpropanoids, straight chain compounds and miscellaneous groups.

Fig. 5 .

 5 Fig. 5. Schematic illustration of the techniques used to produce polymeric nanoparticles.

  investigated the oxidative stability of carvacrol and thymol isolated from Origanum dictamnus L. EO and their mixtures, before and after their encapsulation in egg L-α phosphatidylcholine/cholesterol-based liposomes by differential scanning calorimetry analysis. Results showed the appearance of exothermic peaks related to the auto-oxidation process of the samples. The onset temperatures at which the auto-oxidation process starts were in the following order: Carvacrol (258°C)˂Thymol (273°C)˂Carvacrol : Thymol (302°C) ˂Empty liposomes (362°C) ˂

Fig. 7 .

 7 Fig. 7. Schematic illustration of solid lipid nanoparticles and nanostructured lipid carriers'

Furthermore,

  [START_REF] Bazzaz | Solid lipid nanoparticles carrying Eugenia caryophyllata essential oil : the novel nanoparticulate systems with broad-spectrum antimicrobial activity[END_REF] investigated the antimicrobial activity of SLN encapsulated Eugenia caryophyllata EO against Salmonella typhi, Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans using time-kill methods. Results demonstrated that the SLN formulations were effective in Gram negative bacteria and fungi killing, especially

  investigated the therapeutic effect of NLC containing peppermint EO on infected wound. For in vivo study, two full-thickness wounds with the size of 5mm were created in each mouse and inoculated with Pseudomonas aeruginosa and Staphylococcus aureus. Results showed that peppermint EO-NLC could accelerate wound healing in the infected wound model by reducing the total bacterial count, and increasing neovascularization, fibroblast infiltration, collagen deposition, re-epithelization, and levels of FGF-2 and EGF mRNA expressions when compared to control group. Similarly, Zhang et al. reported a decrease in TGF-b1, MMP-1, collagen I and collagen III levels and an increase in apoptosis cells, caspase -3 and -9 levels after application of Ligusticum chuanxiong EO-loaded liposomes on formed hypertrophic scars in the rabbit ear model (H.Zhang et al., 2012). Furthermore, NLC based on olive oil and loaded with eucalyptus oil promote wound

Table 1

 1

	, the nanoparticles produced by nanoprecipitation process owned
	small particle size, narrow distribution with high EE%. Ianniteli et al. (2011) developed
	carvacrol loaded poly (lactide-co-glycolide) based-nanocapsules with a spherical shape, small
	particle size (209.8 nm) and regular distribution (poly dispersibility index=0.26). Similarly,
	Cymbopogon martini EO was efficiently entrapped in poly (ε-caprolactone) based-
	nanoparticles with an average size of 282.1 nm, zeta potential equal to -27.2 mV and EE% of
	about 99.54 %

Table 1 .

 1 Preparation methods for plant oils encapsulation in polymeric nanoparticles and fine applications.

	658
	Encapsulated	Plant (origin)	Wall material	Physicochemical properties		Biological properties	Application	Ref.
	oil			Size	Z.pot	EE
				(nm)	(mv)	(%)
	Nanoprecipitation method
	Costus	Saussurea lappa	Eudragit RS 100	145	+45	/	Anticholinesterase, anti-	Medicine	(Lammari et al., 2021)
							inflammatory
	Baccharis	Baccharis dracunculifolia DC Eudragit RS 100	151.6	+51.7	99.4	Antibacterial	Food	(Timbe et al., 2020)
	dracunculifolia
	Oregano	Origanum vulgare L.	PCL	158-300	-13.8 to -28.5		Antibacterial	Food	(Souza et al., 2020)
	Palmorasa	Cymbopogon martini Roxb.	PCL	282.1	-27.2	99.54	Antioxidant, antimicrobial	Cosmetic	(Jummes et al., 2020)
	Geraniol	/	PCL	289.3	-26.6	99.88	Antioxidant, antimicrobial	Cosmetics	(Jummes et al., 2020)
	Zataria	Zataria multiflora Boiss.	PCL	192-398 +13.9 to +29.2	75-79	Insecticide	Agriculture	(Ahsaei et al., 2020)
	Thyme	Thymus vulgaris L.	Eudragit L 100-55	153.9	-4.11	52.81	Antioxidant	Food	(Pina-Barrera et al.,
									2019)
		Thymus leptobotrys L.	Eudragit RS 100	144	+80.9	/	Bacteriostatic, fungistatic	Medicine	(El-Asbahani et al., 2015)
		Thymus satureoides L.	Eudragit RS 100	132	81.6	/	Bacteriostatic, fungistatic	Medicine	(El-Asbahani et al., 2015)
		Thymus serpyllum L.	Chitosan	117-226	+27	/	Antimicrobial	Agriculture	(Sotelo-Boyás et al.,
									2015)
			Chitosan	/	/	68	Antimicrobial	Agriculture	(Sotelo-Boyás et al.,
									2017a)
	Sweet orange	Citrus sinensis L.	Eudragit RS100	57-208	+39 to +74	56-96	Antimicrobial	Food	(Froiio et al., 2019)
	Bergamot	Citrus bergamia Risso.	Eudragit RS100	57-208	+39 to +74	28-84	Antimicrobial	Food	(Froiio et al., 2019)
	Rosemary	Rosmarinus officinalis L.	PCL	181-407 +11.6 to +28.3 82.9-84.3 Insecticide	Agriculture	(Ahsaei et al., 2020)
			Eudragit EPO	200	/	59	Antioxidant	Cosmetics	(Silva-Flores et al., 2019)
			PCL	145	-11.0	78.2	Insecticide	Agriculture	(Khoobdel et al., 2017)
			PCL	220	-19.9	99	Antioxidant, antimicrobial	Medicine	(Ephrem et al., 2014)
	Lavender	Lavandula dentate L.	Eudragit EPO	200	/	41	Antioxidant	Cosmetics	(Silva-Flores et al., 2019)
			PEO-b-PLA	10-75	/	70-75	Antimicrobial	Textile	(Popiolski et al., 2016)
	Peppermint	Mentha piperita L.	Cellulose acetate	180	-38	/	Antimicrobial	Medicine	(Liakos et al., 2018)
	Cinnamon	Cinnamomum cassia persl.	Cellulose acetate	150	-40	/	Antimicrobial	Medicine	(Liakos et al., 2018)
	Lemongrass	Cymbopogon citratus DC.	PLA	96.4	/	99	Antifungal	Medicine	(Antonioli et al., 2020)
			Cellulose acetate	200	-36	/	Antimicrobial	Medicine	(Liakos et al., 2018)
			PLA	300	-6	/	Antimicrobial	Medicine	(Liakos et al., 2016)
	Black seed oil	Nigella sativa L.	PCL	230-260	-20 to-30	Oil=84	Anti-inflammatory	Cosmetics	(Badri et al., 2018)
	+					Drug=70
	Indometacin

PLGA: Polylactic glycolic acid; PCL: Polycaprolactone; PLA: Poly lactic acid; PHB: Poly(3-hydroxybutyrate); PEO: poly (ethylene oxide); TAD: 1,2,4-Triazoline-3,5-dione; PHBV: Poly(3-hydroxybutyrate-co-3-hydroxyvalerate); HPC: Hydroxypropylcelullose; HPMC: Hydroxypropylmethylcellulose; PVA: Poly vinyl alcohol; PUFA: Poly unsaturated fatty acids; MUFA: Mono unsaturated fatty acids.

Table 2 .

 2 Nkanga et Preparation methods for plant oils encapsulation in liposomes with their fine applications.

	938
	al., 2019).

939 EPA: Eicosapentaenoic acid; DHA: Docosahexaenoic acid; PUFA: Polyunsaturated fatty acids; PCH: phosphatidylcholine; PEA: phosphatidylethanolamine. 941 942

Table 3 .

 3 Preparation methods for plant oils encapsulation in solid lipid nanoparticles and nanostructured lipid carriers with their fine applications.

	1178
	Encapsulated oil	Plant (origin)	Lipid used	Physicochemical properties	Biological properties	Application Ref.
				Size (nm)	Z.pot (mV)	EE (%)
				Solid lipid nanoparticles
	High pressure homogenization
	Carvacrol	/	Cocoa butter	/	/	/	Antioxidant	Medicine	(Carvalho et al., 2020)
	Geranial	/	Monoterpene	120.1	0	/	/	/	(Zielińska et al., 2020)
			Imwitor® 900K
	Ziziphora	Ziziphora	Percirol ATO5	241.1	-22.6	93	Insecticide	Agriculture	(Jajarm et al., 2020)
		clinopodioides	Campritol 888
	Eugenol	/	Caprylic	332	-18.7	91.8	Anticancer	Medicine	(Garg and Singh, 2011)
			triglyceride
			Stearic acid
		/	Hydrogenated	164.5-172.9	/	/	Antifungal	Food	(McDaniel et al., 2019)
			palm oil
			Coconut oil
	Thymol	/	Hydrogenated	166.4-170.5	/	/	Antifungal	Food	(McDaniel et al., 2019)
	Cinnamaldehyde	/	palm oil	198.0-202.1
			Coconut oil
	Sclareol	/	Compritol	128	-29.3	/	Treatment of metabolic	Medicine	(Cerri et al., 2019)
							disorder
	Chamomile	Matricaria	Stearic acid	542	-35.9	/	Wound healing	Cosmetics	(Gad et al., 2019)
		chamomilla L.
	α-pinene	/	Imwitor® 900K	136.7	/	/	Antimicrobial, antioxidant /	(Zielinska et al., 2019)
			Monoterpene	89.7	0	/	/	/	(Zielińska et al., 2020)
			Imwitor® 900K
	Citral	/	Glyceryl	215.4	/	/	Flavoring agent	Food	(Tian et al., 2018)
			monostearate
			Monoterpene	125.4	0		/	/	(Zielińska et al., 2020)
			Imwitor® 900K
	Gac fruit EO	Momordica	Emulgade	200	/	90	Antioxidant; Anti-aging	Cosmetics	(Mai et al., 2018)
		cochinchinensis					Skin tanning, skin care and
		L.					skin protection
	Frankincense +	Commiphora	Compritol888	113.3	-16.8	80-60	Antitumor	Medicine	(Wang, 2012)
	Myhrr oil	myrrha L.	ATO
	Copaiba oil	Copaifera	Cetyl palmitate	126.06	/	/	Antifungal	Cosmetics	(Svetlichny et al., 2015)
		officinalis L.

  Lippia sidoides EO were found more efficient than ketaconazole, used as positive control, in eradicating Candida albicans, Candida glabrata, Candida krusei and Candida parapsilosis (Fernandes et al., 2008). Aspergillus flavus, Aspergillus parasiticus and Aspergillus nomius. López-meneses et al. (2018) investigated the antifungal and antiaflatoxigenic activities against Aspergillus parasiticus of Shinus molle EO-loaded chitosan nanoparticles. Results showed that the prepared nanoparticles affected the spore's germination

	Aspergillus ochraceus, Aspergillus niger, Aspergillus flavus, Alternaria solani, Rhizoctonia solani, and Rhizopus stolonifer was 200, 200, 200, 100, 50 and 50 ppm, respectively; while for un-encapsulated oil, it was 300, 200, 300, 200, 200 and 200 ppm (Nasseri et al., 2016). Furthermore, the nanoencapsulation enhanced the antifungal properties of copaiba oil against Candida krusei, Microsporum canis, Candida parapsilosis and Trichophyton rubrum with MIC90 values of 250, 1.95, 7.8 and 1.95µg/mL, respectively. In another work study, mutation and hepatocellular carcinoma to the high exposure to aflatoxin which is secondary microparticles encapsulating Recently, many studies related the occurrence of some diseases like teratogenesis, metabolites synthesized by toxigenic fungi:

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

facility, simplicity and reduced high shear. However, it is limited by the high metal 1176 contamination potential, unproven scalability and high energy requirement. 1177 functionalization of the particle surface with special ligands to target specific organs and tissues.

However, to our knowledge, there are no reports in the literature that deal with targeting delivery of plant oils loaded nanocarriers. Such demonstrations would provide a blueprint for the development of new concepts and products in large-scale for broader application.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.