Pr Sylvie Poyatos

Fournel

Sylvie Fournel

Dr May Wantz Merci Au

Dr Lydia Brelot

Dr Corinne Bailly

Dr Jean-Marc Strub

Dr Emeric Wasielewski

Martine Heinrich Merci

Mathilde Bouché

Keywords: N-Heterocyclic Carbene, Platinum, Anticancer, Inorganic Medicine, Nanodelivery

J'aimerai ici remercier les gens qui m'ont aidée et soutenue au cours de ces trois années à Strasbourg et ont rendu cette expérience enrichissante aussi bien scientifiquement qu'humainement. Avant tout, je tiens à remercier chaleureusement le Dr Stéphane Bellemin-Laponnaz pour ses conseils, sa disponibilité et pour m'avoir offert autant d'opportunités qui m'ont permis d'évoluer.

Cette expérience restera inoubliable grâce à la sympathie de l'ensemble des collègues que j'ai pu côtoyer à l'IPCMS. Merci particulièrement à Thierry, Aline, Marco, Maya, Yannick, Julien,

Abstract

Cisplatin and other platinum-based drugs are well established in the fight against cancer thanks to their great cytotoxic activity. However, numerous shortcomings remain to be tackled, namely their low stability, lack of selectivity and resistance of several cancer cell lines to platinum-based treatment. Therefore, improved anticancer drugs are strongly awaited to substitute agents currently used in clinics. N-Heterocyclic Carbene (NHC) appeared as a powerful class of ligands for drug development and their coordination to platinum centre has recently demonstrated very promising results as anticancer agents.

In the aim to access drugs displaying novel mode of action, both electronic and steric environment of the platinum centre have been finely tuned by variation of either its coordination sphere by simple ligand exchange, or the metal oxidation degree to access NHC-Pt(IV) prodrug candidates. Their stability has been explored and their potential at promoting cancer cell death prompted us to conduct a thorough mechanistical investigation on the most promising derivatives. This highlighted the efficiency of NHC-Pt(IV) complexes toward cisplatinresistant cancer cell lines thanks to a mitochondria-mediated apoptosis pathway Furthermore, NHC-Pt complex combination to nanodelivery devices has been investigated in order to improve both their biocompatibility and selectivity toward cancer cells. While NHC-Pt association to biocompatible protein proved convenient, drug encapsulation into liposomes appeared as a more promising strategy to promote safe and efficient drug delivery. Moreover, NHC-Pt grafting on polyethylenimine chains afforded polycationic macromolecules which proved highly efficient at promoting cancer cell death both in vitro and in vivo. Functionalization of the polymeric chain has been explored by combination to targeting peptide or conjugation of chromophores to unravel drug biodistribution and mechanism of action. Finally, we developed biocompatible gold nanoparticles for further conjugation of the cytotoxic NHC-Pt moieties with the aim to ultimately access theranostic devices for combined therapy and tumour imaging. 195 Pt NMR spectroscopy II. NHC-Pt(IV) prodrugs: stability and drug release

Table of Contents

Acknowledgement

Abstract

Table of Contents

I. Synthesis and characterization of NHC-Pt(IV) complexes 1) Synthesis and characterization of [(NHC)PtBr4(pyridine)] complexes 2) Synthesis and characterization of lipophilic [(NHC)PtBr4L] complexes 3) Synthesis and characterization of [(NHC)PtCl4L] 4) Toward oxidation of NHC-Pt(IV) complexes with oxygen-based oxidants 5) C-X activation on NHC-Pt(II) precursors 6)

Résumé étendu

Au cours des dernières décennies, la chimie inorganique médicinale a largement contribué au développement des sciences médicales par le biais des agents de chimiothérapie à base de métaux, des interactions métal-médicament ou encore de l'implication des ions métalliques dans les maladies. La diversité de propriétés des métaux de transition offre de nombreuses possibilités pour la découverte de nouveaux médicaments. Pourtant, bien que des dérivés tels que le NAMI-A, l'auranofin ou le budotitane aient montré des activités anticancéreuses in vitro intéressantes, à ce jour seuls quelques dérivés de platine sont utilisés mondialement en clinique. Le cisplatine reste donc encore aujourd'hui une référence pour le traitement du cancer grâce à sa forte cytotoxicité qui permet un taux de rémission allant jusqu'à 90% dans le cas du cancer de la prostate. Néanmoins, la faible stabilité du cisplatine provoque souvent de nombreux effets secondaires tels qu'une forte nephrotoxicité, ototoxicité ou encore une myélosuppression. De plus, ces effets indésirables sont parfois observés des années après le traitement dû à une mauvaise excrétion du platine. Finalement, les mécanismes de résistance cellulaire -intrinsèque ou acquis-au traitement basé sur le cisplatine restent des limitations de taille pour le traitement des cancers résistants. C'est pourquoi la recherche de nouveaux dérivés de platine anticancéreux a été un champ d'investigation particulièrement actif aussi bien dans la recherche académique qu'industrielle depuis plusieurs décennies. Etonnamment, parmi ces milliers de composés testés, seulement deux nouveaux dérivés de platine sont utilisés mondialement en clinique comme alternative au cisplatine. En conséquence, il est d'une importance capitale de trouver de nouveaux agents anticancéreux innovants.

Les ligands de type carbène N-hétérocycliques (NHC) sont maintenant bien établis dans le cadre du développement de métallo-médicaments grâce à leur facilité de fonctionnalisation. La stabilité chimique et thermique de la liaison carbène-platine donnent lieu à la formation de complexes particulièrement résistants. Considérant les conditions difficiles rencontrées par les médicaments in vivo, la stabilité de la liaison carbène-platine est également essentielle afin d'éviter les interférences dues aux protéines et l'inactivation prématurée de la molécule active.

Les premières études autour de dérivés NHC-Pt(II) anticancéreux ont confirmé le potentiel de cette famille de métallo-médicaments dont les cytotoxicités sont de l'ordre du micro-molaire sur de nombreuses lignées cellulaires cancéreuses. De plus, les récentes études mécanistiques sur les dérivés de NHC-platine ont suggéré un mécanisme d'action anticancéreux différent du cisplatine. Finalement, au vu des propriétés anticancéreuses prometteuses de ces complexes innovants, le développement d'une bibliothèque de dérivés NHC-platine et l'étude de la variation de leurs paramètres physico-chimiques est essentiel dans la recherche de la nouvelle génération d'agents anticancéreux.

La thèse présentée dans ce document se concentre sur les développements effectués autour de la fonctionnalisation de la brique moléculaire NHC-platine pour développer des médicaments innovants agissants selon un mode d'action différent des agents anticancéreux utilisés à ce jour.

Le premier chapitre présente les propriétés et effets secondaires des complexes de platine anticancéreux ainsi que les développements proposés pour résoudre ces problèmes. Par la suite, plusieurs chapitres sont dédiés aux nombreuses fonctionnalisations étudiées, notamment la variation des ligands portés par le platine ou encore la modification du degré d'oxydation du centre métallique. Finalement, la combinaison des entités NHC-Pt à divers dispositifs permettant une libération contrôlée de dérivés cytotoxiques de platine a été l'objet de plusieurs développements dans le but de limiter les effets secondaires et augmenter leur sélectivité envers les cellules cancéreuses.

Le second chapitre de ce manuscrit détaille la synthèse sélective des complexes trans ou cis de formule générale [(NHC)PtX2(pnictogène)] en fonction de la nature du fragment introduit par échange de ligand ainsi que l'évaluation de leurs propriétés anticancéreuses. Ainsi, plusieurs précurseurs de type trans [(NHC)PtX2(pyridine)] ont été synthétisés par déprotonation d'un sel d'imidazolium en présence d'une base, d'un sel d'halogène et de la pyridine. Cette procédure a permis le développement d'une large gamme de dérivés NHC-Pt-pyridine où la variation des ligands halogénés portés par le platine (chlore, brome ou iode) ou bien des motifs présents sur le NHC est effectuée avec de bons rendements. Les complexes ont été obtenus avec de bons rendements et caractérisés par RMN et spectroscopie de masse. La librairie de molécules a été étendue par une méthode d'échange de ligand sur ces précurseurs. En effet, le fort effet trans du NHC affaiblit la liaison platine-pyridine en trans et favorise l'échange de la pyridine par d'autres ligands. Une large gamme d'amines a ainsi été introduite avec succès et les dérivés trans [(NHC)PtX2L] ont ainsi été obtenus avec de bons rendements. Ces post-fonctionnalisations ont permis la variation des propriétés physico-chimiques des dérivés correspondants. En particulier, l'influence de ces fonctionnalisations sur la lipophilicité a été étudiée par la méthode du flacon sous agitation. L'ensemble des dérivés étudiés s'est montrée bien plus lipophile que le cisplatine, suggérant une meilleure absorption de ces dérivés par les cellules cancéreuses.

La procédure basée sur l'échange de ligands a également été étendue au reste de la famille des pnictogènes avec succès. Alors que les ligands dérivés de phosphine sont bien établis dans le domaine de la catalyse, leur utilisation en combinaison avec les complexes NHC-platine reste mineure dans le cadre des applications biologiques. Il en va de même pour les ligands à base d'arsenic ou d'antimoine en raison de leur mauvaise réputation. Pourtant, l'utilisation en clinique de l'oxyde d'arsenic dans le traitement des leucémies a démontré le potentiel de ces dérivés dans la lutte antitumorale. Ainsi, plusieurs ligands dérivés de phosphine, arsine ou stibine ont été introduits par échange de ligand sur les complexes de NHC-platine dans le but d'accéder à de nouveaux dérivés à double action. La caractérisation de ces composés par RMN et diffraction aux rayons X sur monocristaux a révélé une configuration cis vis-à-vis du NHC des ligands à base de phosphore, arsenic et d'antimoine. Cette configuration est remarquable puisqu'elle a systématiquement été observée contrairement aux dérivés de type [(NHC)PtX2(amine)] qui adoptent systématiquement une configuration trans. Alors que l'ensemble des dérivés NHC-platine testés ont montré une cytotoxicité supérieure au cisplatine sur les cellules cancéreuses, ils se sont également avérés être modérément toxiques envers la lignée cellulaire saine. Ainsi, bien que ces composés n'aient pas démontré d'activité synergique entre le platine et les pnictogènes et malgré leur manque de sélectivité in vitro, ces études ont confirmé le potentiel de la combinaison des briques moléculaires NHC-platine avec les ligands dérivés de pnictogène pour des applications biomédicales.

Le troisième chapitre se concentre sur la modification du degré d'oxydation du platine et son influence aussi bien sur la stabilité que la cytotoxicité de ces dérivés. En effet, l'oxydation du platine au degré d'oxydation +IV qui conduit à la formation de complexes de géométrie octaédrique a été proposée afin d'augmenter l'inertie du centre métallique vis-à-vis des échanges de ligands. Cette stabilité accrue envers les protéines et autres biomolécules devrait permettre l'absorption d'une plus grande quantité d'agent anticancéreux par les cellules tumorales et limiter les interactions indésirables. De plus, les complexes de platine(IV) sont considérés comme des « pro-médicaments » qui sont métabolisés à l'intérieur des cellules par bioréduction sous leur forme active platine(II). En conséquence, leur stabilité vis-à-vis du milieu biologique ainsi que leur cinétique et potentiel de réduction sont des paramètres critiques à contrôler pour permettre une libération optimale du principe actif sans inactivation préalable.

Ainsi, une famille de complexes NHC-platine(IV) a été synthétisée par oxydation directe de précurseurs de platine(II) fonctionnalisés avec un faible excès de dibrome pour donner des complexes de formule [(NHC)PtBr4L] (L = ligand azoté). Cette réaction a permis l'oxydation sélective d'une large gamme de précurseurs avec d'excellents rendements. Bien que l'oxydation directe de précurseurs de platine(II) soit hautement modulable, une seconde méthode de synthèse par post-fonctionnalisation de dérivés [(NHC)PtBr4(pyridine)] a été développée afin d'introduire davantage de diversité chimique dans la famille des NHC-platine(IV). Celle-ci repose sur le fort effet trans du carbène situé en position trans par rapport au ligand pyridine qui est rendu labile et peut ainsi être échangé par d'autres ligands d'intérêt. Ainsi, plusieurs ligands comme la cyclohexylamine ont pu être introduits de façon quantitative sur les complexes de platine(IV), augmentant ainsi la lipophilicité et la diversité des dérivés [(NHC)PtBr4L].

Finalement, la famille de complexes de type NHC-platine(IV) peut également être étendue en utilisant l'iode hypervalent PhICl2 comme oxydant. En effet, cet oxydant a permis la synthèse d'une famille de composés de formule générale [(NHC)PtCl4L] avec de bons rendements.

Finalement, d'autres oxydants ont été envisagés dans le but d'accéder à des dérivés de platine(IV) fonctionnalisés par des ligands hydroxo, néanmoins tous les essais effectués se sont conclus par des échecs.

La caractérisation par RMN 1 H des dérivés de platine(IV) a confirmé l'oxydation sélective du centre métallique puisqu'un déplacement général des signaux vers les champs bas a été observé pour l'ensemble des complexes isolés et s'est montré typique des dérivés [(NHC)PtX4L] avec X = chlore ou brome et L = amine. De même, le déblindage des signaux correspondants à la résonnance des carbones en RMN 13 C est caractéristique de l'oxydation du platine au degré d'oxydation +IV. A noter, contrairement aux autre carbones, le carbone carbènique est systématiquement observé blindé à δ 109-120 ppm dans le cas des complexes NHC-Pt(IV). En outre, plusieurs cristaux uniques ont été obtenus par diffusion de vapeur et ont confirmé la structure octaédrique des complexes de type [(NHC)PtX4L] où le NHC est situé en trans du ligand L alors que les quatre bromes font partie du même plan perpendiculaire. De plus, aucune différence significative de longueur de liaison n'est observée en fonction de la nature de l'halogène coordiné. La stabilité d'une molécule est un paramètre important dans le développement de nouveaux médicaments puisqu'elle influence non seulement sa biodistribution dans le corps, mais également les effets secondaires liés à une mauvaise excrétion comme c'est le cas du cisplatine.

Ainsi, une étude de stabilité a été conduite sur plusieurs exemples représentatifs de complexes NHC-platine(IV) vis-à-vis du DMSO qui est couramment utilisé pour solubiliser des dérivés lipophiles pour des applications in vitro. La réaction de l'ensemble des dérivés NHC-platine(IV)

en présence de DMSO/H2O a été observée par spectroscopie UV-vis et RMN 1 L'analyse par spectroscopie UV-vis de la bande à λ = 280 nm correspondant aux transitions ππ* des résidus aromatiques de l'albumine, a confirmé l'interaction avec l'albumine de l'ensemble des complexes NHC-platine utilisés. A noter, l'interaction semble plus forte dans le cas des complexes portant des ligands bromés que pour les complexes fonctionnalisés par des ligands chlorés. Finalement, le bon relargage des médicaments a pu être observé par RMN 1 H, et leurs activités anticancéreuses ont été étudiées in vitro, confirmant ainsi la différence de cytotoxicité marquée en fonction de la nature de l'halogène porté par le métal.

Chapter 1: Introduction

For the past decades, large contribution to medicinal sciences originated from the field of inorganic medicinal chemistry whether it deals with metal-based chemotherapeutic drugs, metal-drug interactions, metal ions in disease and so forth. 1 The large range of properties available for transition metals offers high opportunities for drug discovery. 2,3 However, in the fight against cancer although NAMI-A, 4 auranofin 5 or budotitane 6 depicted high in vitro potencies, to date no non-platinum drug has been approved for worldwide commercialization and cisplatin remains nowadays the reference for chemotherapy. 7

I. Cisplatin

Breakthrough in the fight against cancer arises from the fortunate discovery of cisplatin's potency by Rosenberg 8 and subsequent FDA approval for its use in clinics. Its high potency allows nowadays a cure rate of over 90% in testicular cancer 9 and appeared as a strong alternative in the treatment of ovarian, testicular, lung and bladder cancers. However, limitations due to major side effects and resistance to cisplatin-based treatment are common.

Therefore, research in academy or pharmaceutical industry on platinum-based chemotherapy remains a very active field of investigation. 1

1) Mechanism of cytotoxicity a. Drug uptake

Cisplatin is usually intravenously injected as a saline solution 10 and progressively enters cancer cell following numerous pathways proceeding in parallel, 11 predominantly either passive diffusion through gated channels or active protein-mediated transport. 12,13,14 In particular, various sulphur containing copper transporters 15,16,17 and other proteins such as organic cation transporters (OCTs) 18,19 have been suggested to favourably support platinum cellular accumulation. 20,21,22,23 The pathway for drug internalization in cancer cells impacts its biodistribution and accordingly both electronic and steric parameters at the platinum centre play a critical role in the efficient drug uptake.

Scheme 1: Mechanism for cisplatin passive diffusion

The complex biological environment promotes cisplatin hydrolysis and metabolites formation 24 though analytic techniques as HPLC analysis, 195 Pt NMR 25 or radiolabelled platinum derivatives 26,27 failed to determine their nature due to sublethal platinum concentrations thus preventing in vivo mechanistic studies. Therefore, reactions in aqueous media mimicking the in vivo environment provided most knowledge concerning platinum fate (Scheme 1). While extracellular pH is 7.4 ± 0.1, 28 intracellular pH drops to 6.8 and chloride concentration dramatically decreases down to 4 mM in cells (vs. 100 mM in extracellular medium) thus promoting the formation of the mono-aquated by-product cis-[(NH3)2PtCl(H2O)] + . Subsequent metabolization proved to favour the formation of diaqua species, hydroxo derivatives, hydroxobridged multimers and so forth [START_REF]Synthesized according to procedure C. Yellow solid, 25.6 mg[END_REF][START_REF]Synthesized according to procedure C. Yellow solid, 15.4 mg[END_REF] which are capable to enter nucleus and further interact with DNA. 31

b. DNA as the main target for platinum derivatives DNA has been recognized as the main target for platinum derivatives due to the discovery of filamentous growth in E. Coli which is characteristic of cell division disruption and DNA synthesis inhibition though cell growth remained intact. 8 The accepted mechanism involves platinum coordination through ligand exchange at the nitrogen atom of nucleobases, especially the N7 atom of guanine (G) and adenine (A). [START_REF]Synthesized according to procedure C. Yellow solid, 15.3 mg[END_REF][START_REF]Synthesized according to procedure C. Yellow solid, 15.1 mg[END_REF] Several adducts have been evidenced and quantified, including 1,2-intrastrand d(GpG) cross linking (Figure 1A) and eventually 1,3-intrastrand d(GpTpG) cross linking (Figure 1B). 34 Pt-DNA adducts (t1/2 > 24h for trans-DDP while t1/2 ~ 8h for cisplatin 35 ) and may explain the formation of easily repaired 1,3-intrastrand and interstrand cross-links 36,37,38,39 rather than 1,2-intrastrand cross-links. 40 This observation highlights the great influence of the platinum environment toward both involved its mechanism and subsequent cytotoxicity.

c. Cisplatin adducts with DNA: influence toward cell cycle, repair system and cell resistance recognition by proteins inducing further cycle arrest signal (Figure 3). Cisplatin is well known to induce caspase dependent apoptosis in cancer cells. 41 Indeed, while it appears to be inefficient at inducing cell death at the G1 checkpoint, cell cycle arrest at the G2 checkpoint has been evidenced and supports replication blocking during the S phase. [START_REF]Synthesized according to procedure C. Yellow solid, 8.5 mg, yield 57%[END_REF][START_REF]Synthesized according to procedure C. Yellow solid, 18 mg, yield 52[END_REF] Moreover, the formation of DNA-platinum adducts promotes the deregulation of polymerases which act as a damage recognition factor thus initiating a nucleotide excision repair [START_REF]Synthesized according to procedure C. Yellow solid[END_REF] To note, several studies suggested a correlation between cancer cell lines resistance and their inability to efficiently undergo mismatch repair process. 52,53 Yet, it is noteworthy to mention that contradictory results were obtained in vitro and in vivo 54 thus suggesting the occurrence of a more complex mechanism of resistance. 55,[START_REF]General procedure F was adapted using the precursor 5 (57 mg, 0.082 mmol) and dppe (1 equiv.). White solid, 62.7 mg, yield 86%. 1 H NMR (300 MHz[END_REF]57,58,59 Furthermore, the cellular tumour antigen p53 has a crucial influence in the recognition of DNA damages and can induce transitory stop in the cell cycle before DNA replication [START_REF]Synthesized according to procedure G. Red solid[END_REF] thus preventing mutation replication and ensuring conservation of the genome integrity. Remarkably, numerous cancer cells depict a mutation inactivating the p53 gene and resistance phenomena observed with cisplatin are often associated to the disability of p53 mutated gene to promote cell cycle stop. [START_REF]Synthesized according to procedure G. Red solid, 7.8 mg, yield 99%[END_REF]

2) Stability and side effects

Despite the impressive results obtained with cisplatin for cancer treatment in clinics, its poor stability causing severe side effects remains a major issue. 62 Moreover, additional adverse effects sometimes appear several years after cisplatin administration due to uncomplete platinum excretion. 63 Hepatotoxicity which corresponds to liver tissues necrosis due to disruption of the redox homeostasis 64 and cardiotoxicity which is usually due to both necrosis and degeneration of the cardiac muscle 65,66 are among the most common side effects.

Moreover, nephrotoxicity is related to a large accumulation of platinum in the kidney during excretion and irreversibly damages surrounding tissues. 67 Finally, ototoxicity is a common side effect and not dose-limiting thus causing immediate and permanent deafness or tinnitus.

Remarkably, it is now widely accepted that only 1% of the initially injected platinum drug reaches the nucleus, 68,69 the remaining platinum being bound to thiols such as cysteine, glutathione (GSH), methionine and so forth. 70,71,72,73,74 While such interactions can improve the sensitivity of several cancer cells to DNA damages, 75 development of chemotherapy resistance can also be promoted. [START_REF]Synthesized according to procedure G. Red solid, 9.5 mg, yield 76%[END_REF] Finally, cisplatin is not selective for cancerous cells thus proving highly toxic toward the whole human body and inducing severe side effects. Accordingly, numerous drug combinations with cisplatin are currently under clinical trial and better analogs are awaited with great interest in order to limit or even suppress such unfortunate events. 77

3) Other platinum(II) drugs

Over 4000 platinum derivatives with good leaving groups trans to aminated ligands have been investigated to lower side effects, increase cytotoxicity and selectivity or even facilitate drug administration, yet only a few reached clinical trials. [START_REF]Synthesized according to procedure H. Red solid, 11.2 mg, yield 99[END_REF][START_REF]Synthesized according to procedure H. Red solid, 8.2 mg, yield 99%[END_REF] Scheme 2: Platinum(II) drugs approved in clinics

a. Carboplatin

Carboplatin was developed by Johnson Matthey and further approved in 1989 for worldwide use. While its overall stability is increased thanks to chelate effect of novel oxygen ligand, slower aquation decrease nucleus osmosis. Yet its binding modes proved identical as cisplatin.

Moreover, increased protein binding and drug deactivation appeared linked to the fact that nephro-and neurotoxicity [START_REF]Synthesized according to procedure H. Red solid, 8.8 mg, yield 99%[END_REF] and cell resistance similar as cisplatin were observed, thus limiting its use against several cancers.

b. Oxaliplatin

Second generation drug, oxaliplatin, was available on the market starting from 2002. It appeared as a strong alternative to cisplatin thanks to its improved design promoting both slower aquation rate and improved stability. Moreover, oxaliplatin depicted somewhat lower affinity for deactivation through protein binding. Potency through DNA binding and NER resistance account for its efficiency at overcoming resistance even in cisplatin-resistant cell lines. Finally, clinical tests confirmed its high efficiency in the treatment of colon cancer where no cross-resistance was observed. [START_REF]Synthesized according to procedure H. Red solid, 11.2 mg, yield 97%[END_REF] However, strong neurological symptoms are still deplored after prolonged treatment.

c. Other Pt(II) drugs with promising clinical responses

Nedaplatin is commercialized by Shionogi Pharmaceutical Company in Japan for the treatment of head, neck and testicular cancers. While fewer side effects have been observed, its mechanism of action proved similar and no overall toxicity improvement was perceived. [START_REF]Synthesized according to procedure H. Red solid, 11.0 mg, yield 97%[END_REF] Heptaplatin is used in clinics in South Korea to cure gastrointestinal diseases. It depicted lower side effects than cisplatin in addition to high activity toward cisplatin resistant cancer cells. [START_REF]Synthesized according to procedure H. Red solid, 10.6 mg, yield 99%[END_REF] Lobaplatin, which was developed by ASTA Pharma in Germany, has been approved in China for the treatment of various cancers such as myelogenous leukemia, breast cancer and so forth. [START_REF]Synthesized according to procedure G. Red oil, 10.7 mg, yield 99%[END_REF][START_REF]Synthesized according to procedure G. Red oil, 10.8 mg, yield 99%[END_REF] Finally, the variety of Pt(II) drugs tested for anticancer applications highlighted the importance of the nature of ligands surrounding the platinum centre. Therefore, the coordination of a stabilizing ligand is expected to overcome restrictions related to low stability and major side effects observed with drugs following the structure-activity relationship (SAR). [START_REF]Synthesized according to procedure G. Red oil, 12.4 mg, yield 99%[END_REF]

II. N-Heterocyclic Carbenes

As previously underlined, the ligands electronic and steric parameters have a strong influence toward complexes pharmacological properties, namely solubility, stability and so forth.

Moreover, platinum (II) anticancer drugs translation to clinics remains confronted to cell resistance mechanism. Consequently, the replacement of amine ligands by more strongly bound ligands has been proposed to go beyond the well-established structure-activity and modify the in vivo platinum fate. N-heterocyclic carbenes (NHCs) recently appeared as a powerful class of ligand for metal coordination in numerous fields ranging from catalysis, [START_REF]Synthesized according to procedure G. Red oil, 10.8 mg, yield 99%[END_REF]88,89 photophysic 90 and bioinorganic drug. 91 Indeed, in addition to being easily fine-tuned and available at low cost in large quantity, 92 NHCs unique properties allow them to perfectly adjust reactivity, oxidation state and geometry of transition metals.

1) Electronic and steric properties of N-heterocyclic carbenes

In the late sixties, Wanzlick 93 and Öfele 94 independently reported the successful synthesis of NHC-metal complexes by imidazolium deprotonation and in situ coordination to transition metal. However, the development of NHC ligands remained restricted for years due to failed attempts of free-carbene isolation. A major advance in the field was achieved by Bertrand who isolated the first free phosphino-carbene in 1988. 95,96 Subsequent isolation of the highly stabilized free bis-mesityl carbene by Arduengo in 1991 97 paved the way for the NHCs which are nowadays well-established ligands in numerous fields of investigation. Both steric and electronic properties can be ascertained with the combined use of characterization and calculation methods. 99,100 This has been highlighted using different techniques ranging from measurements of the free carbene pKa, IR spectra of the corresponding Ir-carbonyl complex, calculated Tolman parameter and percentage of buried volume, electrochemical determination of the LEP parameter, in addition to carbenic carbon 13 C NMR characterization as an indicator of the electronic density in the corresponding bis-NHC moiety. 101,102 Remarkably, the replacement of one N-R function by an electronegative sulphur atom in the heterocycle usually gives rise to weaker donor ligand according to the HEP parameter. Likewise, in the case of triazole derivatives, the third nitrogen atom within the aromatic ring appears to decrease donor properties compared to classical NHCs. 103

2) Metal complexes of NHCs

The biological properties of NHC-metal complexes were initially investigated by the group of Cetinkaya in 1996 and highlighted the potential of NHC-Ru(I) and Ru(II) complexes as antibacterial agents. 104,105 This breakthrough paved the way for NHC-metal complexes expansion in the field of bioinorganic drugs. 106,107,108 Accordingly, while NHC-gold complexes have been widely investigated as novel anticancer drug candidates, 109,110 combination of NHC with silver, 111,112 copper, 113 ruthenium, 114 palladium, 115,116 platinum, 117,118,119 and other transition metal depicted promising results either as anticancer drugs or in the treatment of other diseases. 120 Both chemical and thermal stability of the carbene-metal bond toward air and moisture are of great interest in the development of novel drugs to improve the overall stability of metallodrugs. Considering the harsh conditions encountered in vivo, namely highly acidic or reducing media and reactive agents, the C-M bond stability is essential to avoid any unwanted event and prevent premature drug inactivation. The ease of derivatization and fast optimization of NHCs precursors allow fine-tuning of both steric and electronic properties by simple modification of either their backbone or N-substituents. This is of major importance to efficiently adapt the versatility of metal complexes and improve both physicochemical properties and reactivity in biological media. Finally, the bulky and strongly bound NHC ligand is expected to remain attached to the platinum and thus to induce a different mechanism of antitumor action to access polyvalent drugs.

3 A large range of functionalized NHC-Pt(II)-amine complexes have been synthesized in our group following a tuneable and high yielding pathways (Scheme 6). 117,125,126 Indeed, subsequently to one-pot imidazolium deprotonation and coordination to platinum salt, pyridine-ligand exchange allowed easy diversity enhancement. Efficient pyridine displacement was rendered possible by the high trans influence of the carbene which weakens the Pt-N bond. Therefore, postfunctionalization by ligand exchange with various amino acids and peptides has been widely explored. 127 Very promising results were reached with peptide-functionalized complexes which IC50 reached the range of micromolar and in some cases nanomolar concentrations. Moreover, a luminescent complex where emission may be switched on or off depending on the trans ligand has been developed in our group to potentially gain deeper knowledge in the interactions of NHC-Pt(II) complexes with DNA. 117 Post-functionalization on NHC's backbone is also possible by click reaction of an alkyne-NHC-Pt(II) complex with external azide (i.e. Huisgen reaction). 118 The most remarkable example is an oestradiol NHC-Pt(II) conjugate designed to access active targeting and which proved somewhat more cytotoxic than cisplatin in vitro (Scheme 7). 128 Finally, pH sensitive hydrazine or oxime bonds have been introduced on the NHC's backbone to explore selective targeting and controlled release of bioactive ligands. 129,130 Interestingly, while the combination of NHC-Pt complex with metronidazole favourably compared with cisplatin, neither pyrimidium nor urea conjugation promoted dual action in vitro. Until now, all targeted NHC-Pt(II) complexes (Scheme 7) have been tested in vitro and in vivo studies are needed to evaluate their selectivity toward biological receptors. Finally, while the field of NHC-Pt(II) anticancer drugs is very recent, numerous complex architectures have been reported with particularly impressive potencies toward selected diseases such as antileshmanian properties, 131,132 luminescent cores for investigation of the intracellular biodistribution 133,134 or telomeric targeting by G-quadruplex conjugation. 135

III. Platinum(IV) prodrugs

After decades of investigation on complex ligand architecture on Pt(II) derivatives, recently the attention was turned on the nature of the platinum centre and in particular Pt(IV) derivatives. 136,137,138 While it was often considered as a challenger for anticancer activities, it showed very interesting clinical results. Its molecular structure differs from Pt(II) as the d 6 platinum(IV) adopts an octahedral geometry providing increased inertness toward ligand exchange and offers more opportunities for pharmacological properties fine tuning. This improved stability toward biomolecules allows for greater drug uptake and prevent off-target interactions. Platinum(IV) complexes are considered as a prodrug thanks to their metabolization into cells which involves their bioreduction into a pharmacologically active Pt(II) drug. 141,139 This mechanism has been investigated using several techniques such as elemental imaging of single cell, 140 X-ray absorption near edge structure (XANES) 141 and synchrotron radiation-induced X-ray emission (SRIXE) 142 to confirm drug internalization and release. 143 respectively remain major issues. Good antineoplastic activity, oral availability and weaker side effects were reported for LA-12, yet no overall benefit was observed. 146 The highly lipophilic satraplatin (also known as JM-216) based on a modified cisplatin scaffold depicted potencies that compared favourably with cisplatin both in vitro and in vivo. Its bulky cyclohexylamine ligand is believed to more efficiently overwhelm the DNA-Pt adducts repair process, though some resistance features still appeared. 147 Oral administration allowed up to 10-folds increased inhibition of cancer proliferation compared to intravenous administration. 148 In preclinical phase, six different metabolites where identified, the Pt(II) precursor being the most abundant. 149 Up to 93% of the injected satraplatin was found irreversibly bound to plasma proteins. 150 In clinical trials no neurotoxicity, ototoxicity or nephrotoxicity were observed thus emphasizing its clinical benefit. Nevertheless, FDA refused its market launching due to a too low overall survival benefit. 151

1) Pt(IV) in clinical study

2) Strategies developed to access efficient platinum release and high cytotoxicity

a. Oxidation of Pt(II) precursors and further derivatization

So far mostly Pt(IV) complexes following the SAR, [START_REF]Synthesized according to procedure G. Red oil, 12.4 mg, yield 99%[END_REF] namely derivatives functionalized with two cis-amine ligands, and only scarce examples of phosphine derivatives have been reported for chemotherapy. 152,153 This is probably due to the old assumption that among all the requirements to access highly cytotoxic Pt(IV) derivatives, the presence of at least one ligand possessing a hydrogen bond donor function was necessary. 154 Numerous architectures have been investigated for either biomedical application or investigation of catalytic processes and fully reviewed recently. 155,156,160 However, most oxidation pathways rely on oxygen peroxide-mediated oxidation of the Pt(II) centre (Scheme 9). 157 The presence of L ligands with hydrogen bonding substituents has been suggested to be of importance for efficient platinum oxidation. 158 Several examples of [L2PtCl4] complexes were also obtained by use of chlorine gas or hypervalent iodine, which is more easily handleable.

Theoretical investigation of Pt(IV) complexes following the SAR rule highlighted a trend for chloride complexes to be more active than the hydroxide ones. 159 Finally, only few examples deal with the oxidative addition of a C-X bond and its involvement in catalytic processes.

However, in the case of Pt(IV) prodrugs, hydroxo complexes were preferred as starting material for further development warranting either increased lipophilicity or selective binding to cancer cells (Scheme 10).

Scheme 9: Common oxidation pathways for the synthesis of Pt(IV) complexes 160

A large chemistry has been developed around the functionalization of both equatorial -OH ligands by outer-sphere ligand-based reactivity with electrophiles, namely esters or succinic anhydride (Scheme 10), thus opening access to bis-carboxylate or bis-succinate-Pt(IV) complexes. 160 Interestingly, the stereochemistry is retained during reaction with equatorial hydroxo ligands. Post-functionalization of equatorial ligands is the key step for multiple derivatizations with targeting moiety, chromophores or even organic drug binding. 155,156 Scheme 10: Main outer-sphere ligand based reactivity

b. Strategies developed for efficient Pt(IV) prodrug activity

Equatorial ligands post-functionalization allowed large variation of physicochemical properties such as lipophilicity which was suggested to promote high cytotoxicity. 161,162 Fluorescein (FITC) conjugation confirmed Pt(IV) intracellular uptake and subsequent reduction probably due to increased GSH concentration prior excretion through a lysosomal pathway. 163 Similarly, equatorial grafting of bioactive ligands 164,165,166,167 is of interest to promote improved anticancer activity through synergistic effect by Pt(IV) reduction and equatorial ligands release in cellulo.

In the family of dual-action prodrugs, the functionalization of a cisplatin scaffold with two additional dichloroacetate (DCA) equatorial ligands proved conclusive as high potency where observed toward cisplatin resistant cancer cells. 167 A Pt(IV)-chalcone bioconjugate expected to sensitise cancer cells to platinum based chemotherapy effectively induced p53 activation, yet moderate potencies where detected. 168 Ibuprofen was conjugated to cisplatin scaffold and effectively overcame cell resistance though moderate dual-action was observed. 169,170 Remarkably, Gibson highlighted the difference of efficient concentration between organic drugs and platinum based chemotherapy which explains some failure encountered in the use of dualaction prodrugs. 171 Pt(IV) functionalization with targeting moieties 172,173 where developed this way. Accordingly, the improvement of NHC ligands combination to high valent Pt(IV) centre will be discussed in the present manuscript.

Scheme 12: Isolated stable mono-and bis-NHC-Pt(IV) complexes 181,182,183,184,185,186,187,188 Based on this literature overview and in order to enhance the chemical diversity available for NHC-Pt anticancer agents, we aimed at designing NHC-platinum complexes displaying novel metabolization pathways to efficiently circumvent resistance mechanisms. Therefore, modular synthetic pathways based on easy and reproducible reactions have been developed for the improvement of cytotoxic NHC-platinum complexes. The potential of these novel NHC-Pt derivatives at inducing high cytotoxic activity while overcoming mechanisms of resistance associated with cisplatin treatment will be discussed in the two following chapters (2 & 3).

Finally, the combination to nanodelivery devices has been envisioned to improve NHC-platinum uptake while limiting side effects will be emphasized in the chapter 4.

Chapter 2: Exploration of the functionalization of NHCplatinum(II) complexes

The development of modular and versatile approaches to introduce chemical diversity is of great importance in the field of drug development. This chapter details the one-step synthesis of simple platinum derivatives of the general formula [(NHC)PtX2(pyridine)] with X = Cl, Br or I, while varying the electronic and steric properties of the N-heterocyclic carbene. Further ligand exchange strategy has been developed to introduce novel features such as lipophilic amines or pnictogen-based cytotoxic ligands by taking advantage of the labile pyridine in trans position to the NHC. Finally, their anticancer efficiency has been evaluated toward a range of cancer cell lines.

I. Synthesis and characterization of Pt(II)-NHC complexes with nitrogen-based ligands

1) From imidazolium salts to pyridine-Pt(II)-NHC complexes

All imidazolium salt presented herein were synthesized by N-alkylation with halogenoalkanes and purified by recrystallization according to a reported procedure. 189 Subsequent coordination to the platinum centre was achieved according to a straightforward synthesis developed in our laboratory. 117 The reaction of platinum with 1.2 equivalents of imidazolium salt deprotonated in situ by addition of an excess of base with halogen salt in pyridine led to complexes of the general formula [(NHC)PtX2(pyridine)] with X = Cl, Br, or I after one night under reflux.

Subsequent purification by chromatography on silica gel afforded the expected complexes as yellow powders in good yields. This synthetic pathway could be applied to a broad range of derivatives and as detailed below numerous variations could be achieved to enhance diversity. The whole family of [(NHC)PtX2(pyridine)] complexes could be easily characterized by 1 H and 13 C NMR. Successful NHC coordination was ensured by the disappearance of the characteristic resonance peak associated with the imidazolium salt proton on the 1 H NMR spectra. The apparition of a signal around 130 to 140 ppm in 13 C NMR is a signature for the carbene resonance in trans [(NHC)Pt II X2(pyridine)] complexes.

Scheme 14: Yield dependence on halogen ligand

Variation of the halogen coordinated to the platinum centre can be easily achieved according to the procedure detailed in scheme 13 by using sodium iodide, bromide or chloride. The corresponding bis chloride-, bromide-or iodide-platinum complexes 1-2, 3-4 or 5-6 could be isolated in moderate to good yield depending on the nature of the halogen ligand (Scheme 14).

Higher yields obtained for the iodide-complexes can be attributed to the soft characters of both platinum and iodine atoms compared to harder bromine and chlorine. To note, the purification of the chloride complexes appeared somewhat difficult due to the presence of the [Cl2Pt(pyridine)2] impurity which polarity on silica gel was similar to our complex. We next focused on iodide derivatives mostly because they showed better biological activities. 119

Scheme 15: Variation of N-substituents on [(NHC)PtI2(pyridine)] precursors and isolated yields N-substituents have been varied to increase the diversity of precursors available for further oxidation studies. Special emphasis has been placed on lipophilic substituents, namely linear or cyclic alkyl chains in addition to fluorinated alkyl chain in 7-11. To note, the coordination yield drops when increasing the chain length on N-substituents. Moreover, intercalating moieties, namely anthracene in 15 and pyrene in 16, have also been used in order to increase the overall cytotoxicity and allow near UV luminescence for in vitro tracking. For diversity enhancement, the aldehyde complex 13 is of interest as it could be further conjugated to either complementary drug or targeting moieties and allow synthesis of bioconjugated NHC-Pt(IV) complexes.

Scheme 16: Variation of the NHC backbone and isolated yields Modification of the NHC backbone has also been investigated with the aim to fine-tune both the hindrance and electronic density available at the carbene when coordinated to the platinum centre (Scheme 16). Various NHC-Pt(II) complexes that could allow further oxidation of the metal center have been successfully synthesized in good yields as detailed in scheme 16 (17-22).

Neither aldehyde nor ester reactive functions proved sensible to reaction conditions, thus complexes 19, 20 and 22 could be further used for functionalization by oxime ligation or peptidic coupling. Surprisingly, while the complex 19 proved highly stable both in solid state and in solution, similar complexes bearing either benzyl of alkyl chain substituent proved somewhat less stable and led to complex degradation byproducts in solution.

Scheme 17: Platinum complexes bearing porphyrin-modified NHC backbone

The straightforward procedure developed in our laboratory 118 allowed use of more complex ligand precursors since two porphyrin-modified imidazolium salts synthesized by Dr S. Richeter (Institut Charles Gerhardt, Montpellier) efficiently afforded the NHC-Pt(II) complexes 23 and 24

as red powders (Scheme 17). Signal shifts observed in 1 H NMR proved similar to other derivatives of the [(NHC)PtI2(pyridine)] family. To note, the characteristic broad singlet observed at -2.84 ppm in the 1 H NMR spectrum of 23 corresponding to both pyrrolic amine protons confirmed that the porphyrin ring remained metal-free. In 13 C NMR, the carbenic carbon signal was found around 149 ppm in both cases, which suggests a lower electronic density at the carbene compared to complexes of the same family as 5 which were found at around 135 ppm.

Interestingly, the strong electronic delocalization in the porphyrin ring favours a strong absorption up to 550 nm in UV and should therefore be of interest in the aim to unravel mechanistical aspects in biology by time dependent biodistribution and so forth. The formation of homo-bimetallic complexes proved possible starting from bis-imidazolium salts though both complexes 25 and 26 where obtained in moderate yields (Scheme 18). In 1 H NMR, the integration of coordinated pyridine signals confirmed the homo-bimetallic structure rather than chelating coordination on one platinum centre.

Finally, the influence of both thioimidazole and triazole toward the electronic stabilization of NHC-Pt complexes has been explored by coordination of two non-N-heterocyclic carbenes according to the same procedure as described in Scheme 13. Both trans thioimidazol-and triazole-platinum complexes 27 and 28 respectively, have successfully been obtained as yellow powders and proved stable in both solid state and solution. While the replacement or addition of heteroatom in the carbene backbone is expected to provide a difference in electron donation to the platinum centre in 27 and 28 respectively, only moderate signal shift is observed in 1 H NMR compared to the family of [(NHC)PtI2(pyridine)] precursors.

Therefore, the procedure for platinum(II) synthesis proved to easily adapt to a large range of complex architectures and functional groups introduced on the NHC ligand. This allows easy diversity enhancement in the synthesis of NHC-Pt(II) precursors which will be further used for oxidation in NHC-Pt(IV) derivatives.

The

3) Evaluation of the lipophilicity of NHC-Pt(II) complexes

Lipophilicity is a major parameter which has been suggested to favourably impact both drug uptake and cytotoxicity. It can be evaluated by determination of (logP) which corresponds to the concentration ratio of the compound in octanol over water: (logP) = log

[complex]oct/[complex]water P representing the partition coefficient of a molecule between water and the organic solvent). A (logP) of 1.8 is considered as sufficient to allow efficient oral uptake.

Therefore, lipophilicity measurements were conducted for some selected NHC-Pt(II) complexes using the shake-flask method in a mixture of water-PBS with octanol shaken for 72 h at 37 °C.

After additional 24 h for solution equilibration, concentration of the complexes in both phases could be determined by UV absorbance spectroscopy. The calculated (logP) values for selected compounds are reported in Figure 6.

All tested complexes proved far more lipophilic than the cisplatin and thus improved drug uptake is expected to arise. The most lipophilic complex was compound 8 containing a C18 alkyl chain on the NHC backbone with a (logP) value of 0. All formed complexes adopted a cis configuration contrasting with the trans selectivity observed in the case of NHC-Pt complexes bearing nitrogen-based ligands. Easy characterization using 1 H NMR confirmed a full conversion by total disappearance of proton resonance signals corresponding to coordinated pyridine. All N-CH3 and N-CH2 protons are found deshielded compared to their NHC-Pt pyridine counterparts. Moreover, the presence of bulky ligands in cis position seems to restrict the NHC-Pt rotation as evidenced by the desymmetrization of N-CH2 protons, underlying their different environment. [START_REF]Synthesized according to procedure C. Yellow solid, 15.4 mg[END_REF] P NMR also confirmed the cis configuration of the phosphorous atom at the platinum centre by resonance as a triplet signal with 1 JPt-P ~ 3664-3688 Hz. Carbenic carbon signal resonated around ~ 150 ppm in 13 C NMR which accounts as a fingerprint signal for cis-imidazolylidene platinum complexes.

Molecular structures obtained by X-ray diffraction confirmed a square planar geometry at the platinum centre, and the NHC ligand was always found pointing perpendicularly to the square plane, likely to minimise repulsive interactions. All neutral and cationic complexes bearing monodentate ligands adopted a cis conformation with respect to the NHC, as confirmed by crystal structure analysis in Figure 7.

66

The strong trans effect of the carbene is clearly seen on cis NHC-Pt-As complex 52b for example as the Pt-I bond for the iodide ligand in trans position to the NHC [2.6553( 5) Å] is significantly longer than to the arsine atom [2.6295(5) Å]. However, in the case of the complex 51c with antimony, the trans effect of the Sb seems to be slightly higher than that of NHC since trans to the NHC, the Pt-I is 2.6374( 6) Å while trans to the antimony, the Pt-I is 2.6490( 7 Interestingly, using one equivalent of phosphonium salt, only the thermodynamically favoured bis-phosphine complex 54 or 55 could be obtained. This was confirmed by [START_REF]Synthesized according to procedure C. Yellow solid, 15.4 mg[END_REF] P NMR where the coupling constant JP-Pt were of the same order as previously described cis,cis cationic complexes (2196 Hz for 54). Further attempts to synthesize the mono-phosphine complex under milder conditions led to drastic conversion decrease. However, we could isolate few crystals of the expected neutral complex which is the intermediate to generate complex 55 (Figure 8). Both C-Pt bond and Pt-P bond proved in the same range as previously crystallized NHC-Pt-P complexes (dC-Pt = 1.965 Å, dPt-P = 2.253 Å for 55). Remarkably, the Pt-I bond proved longer in trans position to the phosphine than to the NHC and reveals a greater trans effect of the phosphine (dPt-Itrans = 2.6683 Å, dPt-P = 2.6589 Å).

Scheme 22: Synthesis of both cis-cis and cis-trans cationic complexes 56 and 57

Reaction of an excess of pnictogen ligands (up to 10 equivalents) successfully afforded cationic

[(NHC)PtI(PnPh3)2] + [I -] complexes 57a-c in quantitative yield (Scheme 22
). [START_REF]Synthesized according to procedure C. Yellow solid, 15.4 mg[END_REF] P NMR of complex 57a displayed a single signal at 13.06 ppm confirming the equivalence of both coordinated phosphorous. Moreover, the coupling constant of around 2500 Hz was consistent with two trans phosphorous atoms facing each other. The crystallization of cationic NHC-Pt-pnictogen derivatives proved difficult as obtained crystals were of insufficient quality to allow full refinement of the structure by X-ray diffraction. However, basic connectivities could be ascertained when considering the structure in Figure 9 of the complex 57a. Preliminary results suggested a slightly longer carbene-platinum bond in the cationic complex when compared to its neutral counterpart. This could be attributed to the greater steric hindrance around the metal centre due to both triphenylphosphine groups compared to iodide. Bidentate ligand such as DPPE also promoted the formation of cationic Pt complex 56 and neither κ 1 monometallic species nor bridged bimetallic complex were observed. The 31 P NMR spectrum displayed a typical AB system thus suggesting the non-equivalence of both coordinated phosphorous atoms and confirmed by both coupling constants 1 JPt-Ptrans = 2221 Hz and 1 JPt-Pcis = 3306 Hz. 198,199 2

) Anticancer properties of pnictogen-functionalized Pt(II)-NHC complexes

Finally, cytotoxicity measurements were performed to investigate the possible synergistic effect of platinum centre with pnictogen (Figure 10). In this goal, MTS assay was used to measure cell metabolism and determine the half-inhibitory concentration expressed in μM in comparison to cisplatin. Three representative cancer cell lines (HCT116, colon cancer cell; MCF7, breast carcinoma; PC3, for prostate adenocarcinoma) were used to determine the biological profile in distinct environments, especially prostate cancer which is nowadays treated with cisplatin and MCF7 which is poorly sensitive to cisplatin. One healthy cell line (MRC5, human foetus cell lung) served to investigate possible specific targeting for cancer cells of selected drug candidates. To note, cisplatin activity toward healthy cells was not determined in vitro since this drug is known to target cellular DNA without distinction. Interesting activities were obtained for most complexes that exerted similar or higher potencies than cisplatin for selected cancer cell lines. Remarkably, all tested NHC-Pt-pnictogen complexes depicted greater activity toward PC3, and even more significantly toward MCF7 where complexes 51b and 56 were up to 20-fold more active than the cisplatin reference. Results for healthy cells MRC5 treated with our novel complexes proved more mixed since mainly the lipophilic cationic complexes (54, 56 and 57a-c) proved more potent toward cancer. This result might underline the importance of a greater lipophilicity to improve drug uptake. The improved drug uptake of lipophilic drug candidates might explain their greater cytotoxicity toward cancer cells compared to their neutral counterparts. However, while all complexes appeared as efficient alternative to cisplatin in vitro, neither selectivity toward cancer cells nor synergistic effect could be observed.

III. Conclusion

A library of pnictogen-functionalized NHC-Pt(II) complexes have been successfully synthesized and characterized. We encompassed here the versatility of our method for postfunctionalization of NHC-Pt precursors by easy and high yielding pyridine substitution.

Coordination proved highly selective as only trans NHC-Pt-amine complexes were afforded.

Moreover, the cytotoxicity of these derivatives was already ascertained in our group.

Therefore, encouraged by these results, we extended the scope of this modular method to other pnictogens, namely phosphine, antimony and stibine ligands. Remarkably, only cis NHC-Pt-pnictogen complexes were obtained which contrasts with the trans selectivity observed for NHC-Pt-amine derivatives. Cationic complexes could also be obtained by adjusting the number of pnictogen equivalents, thus affording selectively the cis-cis complexes except when using DPPE ligand. Accordingly, cytotoxicity of several selected compounds was established toward a range of cancer cell lines and compared to cisplatine. While no synergistic effect could be observed, all tested NHC-Pt(II) complexes compared favourably with cisplatin. Altogether, these examples highlighted the post-functionalization of NHC-Pt derivatives as a method of choice to generate a library of cytotoxic complexes whose biological features could be easily tuned according to the introduced pnictogen ligands. Although cytotoxic drug candidates were successfully developed, possible in vivo platinum poisoning and deactivation remains a major issue to solve. Therefore, investigation of more inert NHC-Pt(IV) prodrugs has been suggested as a powerful strategy to tackle this problem.

Chapter 3: Novel NHC-Pt(IV) prodrugs: Synthesis and anticancer application

NHCs proved to be valuable ligands in the development of anticancer metallodrugs by improving the overall stability particularly when combined to platinum as highlighted by several groups including us. [117][118][119] Moreover, considering the promising results obtained with Pt(IV) derivatives as evidenced by the number of prodrugs that entered clinical trials, we decided to investigate the potential of platinum(IV) compounds stabilized by NHC ligands. Indeed, while scarce examples were reported for catalysis purpose, positive anticancer effect is expected to arise from this new class of compounds. Therefore, this chapter emphasizes the synthesis of NHC-Pt(IV) complexes and their evaluation as potential anticancer agent. Complexes of the general formula [(NHC)PtX4L] will be considered, X being either chloride or bromide ligand.

Moreover, since many reports suggest lipophilicity to positively affect cytotoxicity, the synthesis has been adapted to include lipophilic moieties. Full characterization will be detailed herein and 195 Pt NMR will be specially emphasized as a highly specific method of characterization.

Accordingly, their potencies will be discussed and compared to cisplatin while considering their respective solution stability. Finally, preliminary biological mechanistic studies will be presented to emphasize the peculiar action mode of these NHC-Pt(IV) prodrugs.

I. Synthesis and characterization of NHC-Pt(IV) complexes 1) Synthesis and characterization of [(NHC)PtBr4(pyridine)] complexes

Complete conversion of [(NHC)PtI2(pyridine)] precursors into the corresponding bromide Pt(IV) species was achieved after 5 minutes exposure with a slight excess of bromine Br2 at 0°C in dichloromethane (Scheme 23). 201 The desired trans [(NHC)PtBr4(pyridine)] complexes could further be isolated in quantitative yield by simple precipitation using pentane. Remarkably, excess of bromine promoted radical bromation as evidenced by the molecular structure presented in the experimental part. Selective bromation at the 4-position of the imidazole ring was observed under these conditions. Therefore, further syntheses were conducted using strictly two equivalents of bromine and a large range of complexes could be synthesized (Scheme 24). All Pt(IV) NHC complexes were stable under air in the solid state or in chlorine solvents. However, the pyridine functionalized Pt(IV)-NHC complexes displayed poor solubility in all organic solvents. Characterization by 1 H NMR showed that all formed complexes displayed a general signal shift to lower field which proved typical for such [(NHC)PtBr4L] complexes. To note, the resonance signals were found shifted of up to 0.9 ppm for protons in ortho position of the pyridine compared to their NHC-Pt(II) precursors. Moreover, typical features were also noticed leading to more complex signal splitting patterns due to coupling with the 195 Pt isotope.

As expected, chemical shifts to lower field were also observed by 13 C NMR spectroscopy while carbenic signals were observed at ca. δ 109-120 ppm. To note, the signal shift in 13 C NMR corresponding to the carbenic carbon proved higher in the benzimidazole derivative 68 with δC-Pt = 133.9 ppm compared to other NHC-Pt(IV) complexes which range around 110-120 ppm. Due to the low solubility of 72, 1 H-13 C HMBC were recorded instead or regular 13 C NMR and no information could be obtained for the carbon resonance peak corresponding to the carbene. Remarkably, when comparing the NHC-Pt(IV) complexes with their Pt(II) counterparts, it appeared that both C-Pt and Pt-N bonds were longer in the octahedral NHC-Pt(IV) form than in the square planar NHC-Pt(II) complexes (typical value was dC-Pt = 1.97 Å in Pt(II) and raised in Pt(IV) to dC-Pt ~ 2.05 Å). Similarly, the N-Pt bonds which elongate from dN-Pt = 2.09 Å in Pt(II) to dC-Pt = 2.12 Å in Pt(IV) which is consistent when considering the bulk increase around the metal due to two additional ligands.

2) Synthesis and characterization of lipophilic [(NHC)PtBr4L] complexes

As for NHC-Pt(II) complexes, it appeared that the labile character of the pyridine trans to the NHC could be exploited to perform ligand exchange and allowed easy diversity generation in NHC-Pt(IV) metallodrug candidates (Scheme 27). Therefore, the use of selected amines as solvent efficiently afforded quantitatively the corresponding [(NHC)PtBr4L] complexes as red oils. The disappearance of signals corresponding to the coordinated pyridine in 1 H NMR accounted for the complete ligand exchange while the proton resonance peak of N-CH3 at ~ 3.8 ppm confirmed that the Pt(IV) centre was not reduced.

Scheme 27: Post-functionalization with lipophilic amine as ligands (97-99% yield) Although more lipophilic NHC-Pt(IV) complexes could successfully be obtained using neat conditions, only a few range of amines are available as liquid at room temperature, thus limiting the functional diversity available. Therefore, the synthetic pathway involving oxidation of NHC-Pt(II) precursors functionalized with butylamine, dodecylamine and so forth (29-50) As expected, selected lipophilic amines proved inert toward bromation under reported conditions, thus allowing large variations at the platinum centre. Most protons signals in 1 H NMR were found slightly shielded of around 0.1 ppm in the case of primary and secondary amines 77-92 compared to their [(NHC)PtBr4(pyridine)] counterpart 64. To note, oxidation of the cis NHC-Pt(II)-pnictogen derivatives promoted the concomitant formation of numerous species and neither increased dilution nor longer reaction times favoured the formation of a single isomer. Furthermore, (logP) measurements have been carried in order to evaluate the lipophilicity of selected NHC-Pt(IV) complexes and compare with their Pt(II) counterparts.

However, due to Pt(IV) reduction occurring concomitantly to the 72 h stirring in octanol/water solution, no clear results could be obtained.

Two NHC-Pt(IV) complexes bearing lipophilic amines 77 and 81 respectively were grown as single crystals suitable for X-ray diffraction studies by slow diffusion in pentane/dichloromethane (Figure 12). Akin to their counterparts bearing a pyridine moiety, both complexes selectively adopted a distorted octahedral geometry with the amine ligand in trans position to the NHC. Remarkably both Pt(IV) complexes displayed significant bonds elongation compared to their Pt(II) precursors, evidence of the steric prevalence toward electronic parameters. 202 However, the N-Pt bond distance did not vary much depending on the σ-donation of the amine ligand. The interaction between the shortened bromine and the empty p orbital at the carbene was even more pronounced for 77 where the distance is 3.182 Å. On the contrary, in 81 no Pt-Br bond length elongation was noticed, yet slight interaction with the carbene was still noticed with a distance through space of 3.238 Å.

A) B) In conclusion, a wide range of [(NHC)PtBr4L] complexes could be successfully synthesized in high yield by direct oxidation of NHC-Pt(II) precursors bearing diverse functional groups and fully characterized. The molecular structure of several representative complexes functionalized with lipophilic amines confirmed their octahedral geometry and the oxidation with bromine proved regioselective as only trans complexes were observed by X-ray diffraction.

3) Synthesis and characterization of [(NHC)PtCl4L]

Remarkably, a majority of platinum complexes that entered clinical trials are decorated with chloride ligands 4b rather than bromide. Access to the chloride family [(NHC)PtCl4L] proved successful by oxidation using the freshly prepared hypervalent iodine reagent PhICl2 203 again in excellent yield (Scheme 29). The mechanism is supposed to involve light activated dissociation of a chlorine radical and subsequent oxidation at the platinum centre. 204 The expected [(NHC)PtCl4(pyridine)] complexes were isolated as light yellow powders by precipitation with pentane. All [(NHC)PtCl4L] complexes displayed overall signals deshielding in both 1 H NMR and 13 C NMR, similarly to their bromide counterparts, though the observed shift is less significant since ortho protons on the pyridine moiety and N-methyl protons are found deshielded up to 0.6 and 0.4 ppm respectively compared to their Pt(II) precursors. To note, these pyridine functionalized Pt(IV)-NHC complexes proved poorly soluble in all organic solvents and thus characterization by 13 C NMR proved difficult. Still, interesting trends could be observed as carbon signals deshielding except for the carbenic carbon which was found around 110 to 115 ppm as previously underlined in section 3.I.1 for bromide complexes. To note, the oxidation step proved somewhat more sensitive to the platinum environment and surrounding ligands when using hypervalent iodine compared to bromine. Difficulties in the oxidation of NHC-Pt complexes using iodobenzene dichloride have already been reported by Strassner who failed in oxidizing a cationic tetra-NHC platinum complex with bromine as the counter-ion. 205 The formation of Br-Pt(IV) derivatives is very likely to be preferred to Cl-Pt(IV) for and 97 were afforded in good yield and similarly to their bromine counterparts 64 and 73, benzylic protons for both complexes 94 and 98 appeared as singlet in 1 H NMR. Moreover, while 99 proved easily oxidized and stable for over a week in chlorine solvents, 94 was somewhat less stable and quickly decomposed in solution within days. Finally, the homobimetallic complex 101 could be obtained similarly also in high yield. Unfortunately, the range of functional groups stable under oxidative addition remained limited since neither precursors bearing ester 8 and aldehydes 11 and 18 nor NHC-Pt(II) complexes bearing anthracene 13 and pyrene 14 could be oxidized without the formation of numerous by-products. Finally, the oxidation using PhICl2 of both thioimidazol-and triazol-complexes 23 and 24 respectively proved difficult and only complex mixtures were observed. Moreover, the rapid reduction of NHC-Pt(IV) complexes into their Pt(II) counterparts on silica gel, emphasized above prevented purification through column chromatography and recrystallization attempts were unsuccessful.

The direct oxidation of Pt(II) precursors bearing lipophilic amines using PhICl2 following the same procedure as their pyridine counterparts successfully afforded the highly soluble [(NHC)PtCl4L] complexes 102-106 (Scheme 31). Although complete conversion of Pt(II) precursor was observed by 1 H NMR, the lipophilic complexes 104-106 were isolated in moderate yield probably due to their low solubility in pentane, thus preventing full complex recovery even by centrifugation.

Scheme 31: Lipophilic and highly soluble [(NHC)PtCl4L] complexes

Comparison between 1 H and 13 C NMR spectra of both NHC-Pt(IV) complexes and their precursors highlighted similar trends as their pyridine counterparts with an overall signal deshielding of up to 0.6 ppm. Again, carbenic carbons were found shifted of over 30 ppm to higher field suggesting an increased electronic density at the carbene. 4), 177.34 (12); Cl(1)-Pt(1)-Cl( 4), 91.85 (12).

Moreover, single crystal of the [(NHC)PtCl4(pyridine)] complex 94 could be grown by slow diffusion in pentane/dichloromethane. Its molecular structure confirmed the octahedral geometry around the Pt(IV) centre surrounded by the four chloride ligands in a slightly distorted square plan. No major modification of the overall structure is observed compared to the bromide complex 64 (Figure 11), suggesting chloride ligands to have little impact on the whole structure. Only C-Pt bond is smaller than in bromide counterpart according to chlorine's smaller

Van der Waals radii with dC-PtBr = 2.066 Å and dC-PtCl = 2.034 Å. 18 H-bonding network was observed between N-substituents protons or ortho-pyridine protons and the four chlorine atoms.

In conclusion, several complexes of the general formula [(NHC)PtCl4L] could be obtained and characterized; their physico-chemical and antiproliferative properties will be emphasized below in Section 3.II.1.

4) Toward oxidation of NHC-Pt(IV) complexes with oxygen-based oxidants

The majority of reports dealing with Pt(IV) drugs are based on the oxidation of cisplatin scaffold using hydrogen peroxide, yet neither diluted nor freshly concentrated H2O2 solution succeeded in oxidizing our selected NHC-Pt(II) precursors. 207 No positive influence could be observed when exposing the reaction mixture to light, higher reaction time or temperature. Similar behavior was already reported on bis-phosphine complexes 208 and the suggestion that proximate ligands promoting hydrogen bonding are necessary for successful oxidation with H2O2 might explain this failure. 209

Scheme 32: Unsuccessful attempted oxidation of NHC-Pt(II) precursors using hydrogen peroxide Many other one-or two-electron oxidants have been tested namely PhI(OAc)2, 210 TEMPO, OXONE, tBuOOH, KMnO4, HClO4 and so forth, though oxidation met with failure in all cases.

Several strategies were envisioned to favor halogen replacement by oxygen-based ligands, namely in situ deprotonation of chelating ligands like acac, halogen abstraction by silver triflate or freshly synthesized silver malonate salt. However, all attempts met with failure as the redox reaction prevailed and only Pt(II) product could be isolated concomitantly with degradation.

Scheme 33: Unsuccessful ligand exchange with silver malonate salt on NHC-Pt(IV) complex 87

Reasons explaining the failure of oxygen-based ligands coordination to NHC-Pt complexes remain unknown at the moment and could be due to either steric or electronic parameter.

Hence, post-functionalization with free carbene as reported by Steinborn could be a fair solution, otherwise electrochemical synthesis could be envisioned in the future. 184

5) C-X activation on NHC-Pt(II) precursors

As presented in the introduction, literature reports on NHC based Pt(IV) complexes mainly deal with spontaneous oxidative addition of a C-X bond. However using similar procedures, none of the trans [(NHC)PtI2(pyridine)] precursors investigated successfully promoted activation of trimethylsilyl bromide, methyl iodide, methyl magnesium bromide or 5-(trifluoromethyl)dibenzo-thiophenium tetrafluoroborate even after up to 96 h reaction. processes in serum media. However, drug stability should be investigated prior in vivo investigation to confirm its inertness until it reaches its target. Best-selling cisplatin is an interesting illustration of the issue encountered with platinum drug due to its interaction with the solvent and poor stability in the blood stream. 214,215 Indeed, numerous side effects noticed after the injection of cisplatin are partly due to its poor stability in biological environment.

Moreover, in drug screening, stock solutions are often prepared using DMSO as solvent at high

concentration. Yet, the highly nucleophilic sulfur atom from DMSO is able to coordinate numerous metals by ligand displacement. Such unfortunate event is not only damageable due to structure modification so as electronic and steric change, but more importantly can affect drug's cytotoxicity and biodistribution. Indeed, DMSO has been shown to lower the potency of cisplatin toward cultured thyrocytes 216 and several reports recently stressed the importance to evaluate the possible interaction between investigated drug candidates and DMSO. 215,217,218 Therefore, prior to investigation of anticancer properties, the stability of selected NHC-Pt(IV)

complexes have been evaluated toward a DMSO/H2O solution.

Scheme 35: Stability of (NHC)PtX4(amine) complexes in DMSO/H2O (C = 10 -3 M, 20°C)

It appeared that both families of NHC-Pt(IV) complexes reacted in the presence of DMSO to form new NHC-Pt(II)-DMSO species which were isolated and compared to synthetically obtained [(NHC)PtX2(DMSO)] complexes 107 and 108 (X = Br, Cl). This evolution could preliminary be studied by UV and 1 H NMR measurement on a 8 mmol solution of the selected complex in a 4/1 solution of d6-DMSO/D2O until full NHC-Pt(IV) consumption. Conversions were calculated based on the signal integration corresponding to pyridine protons in ortho position (Figure 16). The reduction of NHC-Pt(IV) complexes could be precisely followed by either decrease in UV of the band λ = 359 nm or by 1 H NMR analysis in which disappearance of the resonance peak for ortho protons of coordinated pyridine and apparition of free pyridinium signal attested for the formation of Pt(II)-DMSO compound 108 (Figure 16). To note, the less coordinating solvent DMF is usually a great alternative to DMSO in the preparation of stock solutions, however as already discussed the low solubility of our NHC-Pt(IV) prodrug candidates in DMF prevented its use as alternative solvent.

The stability of NHC-Pt(IV) complexes in biological media has been evaluated by solubilizing the selected complex 59 in mouse serum at 37 °C for 72 h. However, 1 H NMR on the extract proved inconclusive due to the multiple proteins overlapping characteristic NHC-Pt(IV) signals. A secondary followed-up experiment has been performed using UV-vis spectroscopy in a mixture of 9/1 of DMSO/mice serum containing the complex 59. The band intensity decrease at 380 nm suggested a full consumption of the NHC-Pt(IV) prodrug candidate within 30 minutes, which is reasonable for further use in biological application since the half-life stability in blood of cisplatin is t1/2 = 21.6 min 221 while satraplatin is t1/2 = 6.3 min. 222 MALDI mass analysis failed at giving additional insight on the formed metabolites as only heavy protein fragments were observed which might suggest complex trapping into the hydrophobic cavities of proteins as already evidenced for cisplatin 223 and other platinum compounds. 224,225,226 Similarly, in 195 Pt NMR no signal corresponding to the NHC-Pt(IV) complex 59 or its reduction product 107 could be observed, which might suggest the formation of other metabolites or trapping of the complex into protein thus disturbing signal acquisition.

2) Investigation of the NHC-Pt(IV) reduction process by biological reducing agent

It is nowadays widely accepted that a two-electron bioreduction of Pt(IV) prodrugs in vivo is necessary to release the active drug and promote anticancer activity toward cancer cells (Figure 18). 227,228 As previously reviewed in the introduction, numerous sulphur containing molecules and proteins encountered within the serum and hypoxic tumors can be responsible for the Pt(IV)/Pt(II) redox process. 229 Reduced glutathione (GSH) is a common reducing biomolecule largely present in the blood with a concentration in healthy patients is ranging around 680-2500 μM in the blood and 2-11 μM in the plasma. Moreover, only the reduction product [(NHC)PtX2(pyridine)] was observed by 1 H NMR, thus suggesting that no GSH-Pt adduct formation occured in parallel to the bioreduction which contrasts with platinum poisoning reported for cisplatin. 235,236,237 To note, while GSH failed at displacing the pyridine ligand, smaller thiols as the ethylthiol proved to bind NHC-Pt complexes, suggesting great influence of the steric parameter toward coordination.

Other biological reducing agents have been evaluated for the bioreduction of NHC-Pt(IV) prodrug candidates, namely ascorbate which concentration in blood plasma is 50-150 µM 238,239 and methionine, under similar conditions and in a 1/1 ratio of Pt/reducing agent. Again, only the expected NHC-Pt(II)-pyridine compound was formed and no side reaction occured contrarily to the group of Natile which noticed a dependence of the reduction product upon the nature of reducing bio-molecule. 240 Moreover, slower reduction was observed for both methionine and ascorbate compared to the GSH which is coherent with literature. 241 prodrugs reported which reduction kinetic is rather of the order of minutes than hours. 242,243,244 Therefore, these investigations validated the possibility of drug release in great time scale of [(NHC)PtCl4(pyridine)] compounds in a solution mimicking biological media. Moreover, NHC-Pt(IV) prodrug candidates appeared to be sufficiently kinetically inert to prevent early hydrolysis and other unwanted side reactions with biological material.

3) Electrochemical investigations

Potency In order to gain more insights on the reactivity of NHC-Pt(IV) complexes in DMSO, cyclic voltammetry has been performed in DMSO using the same parameters as previously mentioned above (Figure 22). While no reduction potential modification was observed for 95 when solubilized in either acetonitrile or DMSO, drastic reduction potential shift was observed for 59

as Ered = -0.55 V in acetonitrile and goes up to Ered = -0.4 V in DMSO (Figure 21). This suggests that 59 is more easily reduced in DMSO compared to other solvents and confirms the observed rapid reduction in DMSO/H2O solution observed by 1 H NMR and UV-vis.

1) Cytotoxicity of selected NHC-Pt(IV) prodrug candidates

The anticancer activities of some selected NHC-Pt(IV) compounds (Scheme 37) have been evaluated in vitro toward three human cancer cell lines, namely HCT116, MCF7 and PC3 treated at several platinum concentrations for 72h and compared to cisplatin (Figure 37). The percentage of viable cells was determined by MTS assay and allowed measurement of half inhibitory concentration (IC50) defined as the maximal concentration of a drug needed to inhibit a given biological process by half. All experiments were performed in triplicate at Imagif, Gif sur Yvette (Chapter 5). on the three cancer cell lines and 102 was even found one order of magnitude more active than the cisplatin. Only the complex 106 bearing a polyethyleneglycol chain in trans position to the NHC appeared to be less active than other tested chloride NHC-Pt(IV) complexes. Remarkably, results presented in Figure 25 did not suggest improved potencies along with the greater lipophilicity. However, this has already been reported for other Pt(IV) complexes and a more comprehensive drug screening would be necessary to disregard the lipophilicity as a valuable parameter to tune for efficient NHC-Pt(IV) drug development. 245 The family of [(NHC)PtBr4L] complexes depicted mixed activities and were typically found ranging around ~ 5-15 µM. The MAL-functionalized complex 91 which was tested under regular conditions for biological analysis promoted moderate cytotoxicity as IC50 = 35-39 µM toward the three cancer cell lines. 107 However, no complementary experiment exposing the cancer cell lines to a source of light has been undergone, which might result in higher potencies thanks to photodynamic therapy on the MAL moiety and its metabolites. The complex bearing an aldehyde-functionalized NHC backbone 66 appeared even less cytotoxic depicting only moderated anticancer activities.

However, such results were not unexpected considering the somewhat modest stability of the bromide NHC-Pt(IV) family discussed above. Indeed, both 107 and 108 complexes bearing a DMSO moiety are not toxic under tested conditions up to 100 µM. sensitive to platinum based chemotherapy. Several [(NHC)PtCl4L] complexes proved significantly cytotoxic, some of them appearing even more potent than their Pt(II) precursors, thus suggesting the occurrence of complementary anticancer pathways to a simple reduction into Pt(II). Accordingly, more work is necessary in order to stabilize the bromide family and envisioned strategies to achieve it will be further exposed in chapter 4.

2) Efficiency of NHC-Pt(IV) complexes toward cisplatin resistant cell lines

Altogether, previous results highlighted the potential of NHC-Pt(IV) complexes as effective anticancer agents toward several human cancer cell lines, yet the major issue in the field of platinum-based chemotherapy remains the acquired and intrinsic resistance of cancer.

Therefore, to determine whether NHC-Pt(IV) could substitute cisplatin in the treatment of resistant cancers, the cytotoxicity of prodrug candidate 95 has been evaluated toward both As expected, the cytotoxicity of cisplatin toward the resistant cell line A2780R is reduced by almost a factor two compared to A2780, thus confirming the drug inefficiency at providing complete anticancer activity when the caspase-3 dependent apoptosis pathway is inactivated.

On the contrary, the treatment of A2780 cell line with our complex 95 seemed of the same order toward the resistant cell line A2780R as A2780 (IC50A2780 = 6.17 µM and IC50A2780R = 3.36 µM). Moreover, the resistance factor calculated as R = IC50A2780R/ IC50A2780 proved to be below 1 (R95 = 0.54) thus confirming that compound 95 efficiently overcomes this mechanism of acquired resistance. Therefore, altogether these results pointed out the efficiency of 95 toward cisplatin resistant cancer cell line A2780R and would need to be confirmed toward a larger range of cisplatin resistant cancers. Moreover, more solid investigations would be necessary to confirm a caspase-3 independent pathway for the cytotoxicity of 95. The caspase-3 apoptosis pathway is supposed to be activated through a p53-mediated cell death, 247,248,249 p53 being a tumour antigen supposed to preserve genome integrity by inducing cell cycle stop at the G1/S phase and subsequent apoptosis. 250,251 Therefore, a complementary mechanistic investigation has been performed in collaboration with Pr S. Fournel (Faculté de Pharmacie de Strasbourg) to determine whether NHC-Pt(IV) complexes promote their anticancer activity through a p53 dependent pathway. The cancer cell line HCT116p53KO where the p53 gene is rendered inactive has been treated alternatively with our complexes 59 and 95

or oxaliplatin serving as a reference for clinically used chemotherapy. The inhibition percentage appeared to be within the same range between blanc sample and platinum chemotherapy reference oxaliplatin which suggests that oxaliplatin failed at inducing cancer cell death when the p53 pathway is inactivated thus confirming its inefficiency at overcoming resistance phenomenon. On the other hand, both NHC-Pt(IV) complexes seemed to promote cell inhibition of the same order toward p53 deficient cancer cells (Figure 28), though IC50 values previously reported on HCT116 suggested the chloride complex 95 to promote greater anticancer activity than 59 (IC50 = 1.48 µM for 95 and IC50 = 5 µM for 59). Finally, these results supported that NHC-Pt(IV) complexes behave following a different pathway from cisplatin-like drugs and thus might be promising anticancer drugs to overcome resistance associated with cisplatin.

3) Binding experiments

Numerous reports highlighted DNA as the primary target for cisplatin and the formation of platinum-DNA adducts has for long been admitted as the major event responsible for its high in vivo cytotoxicity. Interestingly, several groups already suggested Pt(IV) to be capable to bind nucleobases. 252,253,254 Therefore binding experiments have been undertaken with two selected NHC-Pt(IV) complexes 59 and 95 which have been reacted in either ethanol or DMSO or DMF solutions with one equivalent of either guanine or adenine at 37 °C for 96h and compared to their Pt(II) precursor 6. 1 H NMR analysis of the extract revealed that no nucleobase coordination occurs at the platinum centre for 59 and 95 and instead a mixture of reduction products and starting material are obtained in all cases, so as the low valent platinum complex 6. Others have already reported similar trends in the chemistry of platinum-based complexes 255,256 though several reports of Pt(IV)-mediated nucleobase oxidation are found in literature. 257,258,259 Accordingly, these preliminary results should be considered cautiously according to the Finally, though the cytotoxic NHC-Pt compounds failed at binding nucelobases, other cellular compartments might be preferred targets for NHC-Pt(IV) complexes than DNA.

4) Mitochondria as an alternative target: from ROS generation to mitochondria dependent cytotoxic pathway

Mitochondria is the cellular compartment in charge of cells respiration and furnishes energy to cells through glucose oxidation. Oxidative stress in cellular tissue is a common process that lead to oxidative damage 260 by redox homeostasis disruption in the mitochondria and has been widely exploited in the field of metal-based anticancer drug. 261 Transition metals and particularly platinum drugs like cisplatin 262 or Pt(IV) derivatives 263,264,265,266,267 contribute to the death of mitochondria by in situ generation of radical oxygen species (ROS), namely superoxide (O2 •-), hydrogen peroxide (H2O2), hydroxyl radical (OH • ) and so forth. 268 Platinum derivatives also disturb the redox balance by interacting with the glutathione thus promoting cell cycle disruption and apoptosis. 269 Therefore, oxidative stress investigations have been undertaken on two selected NHC-Pt(IV) compounds 59 and 95 in addition to the NHC-Pt(II) complex 6, and compared to oxaliplatin and staurosporine as a reference for ROS active drugs. 270 HCT116 cancer cells were treated with selected drug candidates at various concentrations for 13 h at 37

°C and subsequent incubation with MitoSox a mitochondrial superoxide indicator allowed quantification of cells whom mitochondria express ROS. µM). Moreover, they appeared to be dose-dependent since important increase in ROS sensitized cells was observed at 100 µM (up to two-fold more positive cells than staurosporine), though no significant increase in ROS production was detected for NHC-Pt(IV) derivatives 59 and 95 compared to the NHC-Pt(II) complex 6. In addition, only negligible effect is observed in cells treated with oxaliplatin, thus confirming a cancer cell death pathway that did not involve mitochondria. These results confirmed the mitochondria as a target for platinum-NHC based cytotoxicity since high stress levels were observed. Finally, the family of NHC-platinum complexes proved to successfully induce anticancer activity according to a different pathway from the clinically used oxaliplatin, therefore highlighting their potential in the treatment of cisplatin-resistant cancers.

IV. Conclusion

This chapter emphasized the synthesis of a library of high valent NHC-platinum prodrug candidates. Several straightforward synthetic pathways have been described herein to allow easy and modular access to a range of [(NHC)PtX4L] derivatives with X corresponding to either bromide or chloride ligand. We also extended the scope to highly lipophilic NHC-Pt(IV)

complexes by taking advantage of the trans pyridine lability. Characterizations are reported with special highlight on the use of 195 Pt NMR which proved to be a powerful tool in the evaluation of the platinum environment in both NHC-Pt(IV) and NHC-Pt(II) complexes. A full investigation of their stability properties toward DMSO and toward selected reducing bio-molecules validated the concept of prodrugs. The potency of this innovative family of complexes was evaluated toward several cancer cell lines and proved generally more active than the clinically used cisplatin. Encouraged by these results, a comprehensive investigation of mechanisms involved in their cytotoxic activity has been performed. Selected derivatives revealed promising efficiency at promoting cancer cell death in several cisplatin-resistant cell lines and a mechanism involving stress generation in mitochondria has been uncovered. Thus, we generated a chemical library of cytotoxic NHC-Pt(IV) prodrug candidates with promising potencies toward both regular and cisplatin resistant cancer cells.

Chapter 4: Nanodelivery of NHC-platinum complexes

Side effects associated to cisplatin-based cancer treatment have been suggested to arise from the formation of protein-platinum adducts which disrupt biological processes. 272,273 Therefore, nanodelivery devices have raised a huge interest to limit side reactions and access highly cytotoxic and biocompatible drugs for selective cancer targeting and individualized treatment. 274 However, numerous parameters are highly dependent on the nanoparticle choice, namely the route of administration, the mechanism for drug release and so forth. Therefore, we describe here four strategies to combine the cytotoxic NHC-Pt moieties to nanodelivery devices with the aim to improve selective drug uptake and lower side effects. The first part deals with NHC-platinum complexes covered by a biocompatible protein. The synthesis, characterization and drug release were then explored to ascertain the efficient drug delivery to cancer cells.

Finally, their biological activities have been investigated and compared to free drugs. The second part of this chapter emphasizes preliminary developments of a liposomal formulation for NHC-platinum drugs and their anticancer activities. The next part is dedicated to the synthesis and comprehensive biological evaluation of biocompatible polymers functionalized with cytotoxic NHC-Pt moieties. Several synthetic pathways were used to enhance diversity by combination with chromophore or targeting moieties and their anticancer activity will be discussed. Finally, the synthesis of gold nanoparticles and preliminary investigation of their biocompatibility are detailed along attempts of drug conjugation.

I. Proteins as biocompatible carrier

Among dozens of proteins known to bind cisplatin and other platinum based complexes, human serum albumin (HSA) is of importance. Indeed, albumin is the main blood protein and regulates osmotic blood pressure. 275 HSA usually binds a large amount of injected platinum, 276 and this

Chapter 4 Nanodelivery of NHC-platinum drugs 118 strong affinity has been exploited for numerous applications ranging from surface functionalization, biosensors, deactivation of selected proteins relevant for defined pathologies and so forth. 277 However, large proteins can also be used as drug carrier to improve its circulation time in blood and tumour accumulation thanks to the enhanced permeability and retention effect (EPR). 278,279 Therefore, taking advantage of the high affinity of platinum complexes for albumin, its use as a biocompatible cargo for hydrophobic NHC-Pt complexes has been investigated herein to access selective drug delivery. 280,281 ) and composed of a single chain of 585 amino acids. 284 This protein is in charge of osmotic blood pressure regulation as well as lipids transport. The Sudlow's site I in HSA is known as a common locus for interaction with hydrophobic drugs such as cisplatin. 285,286 Yet contrarily to

1) State of the art: albumin in drug delivery

Chapter 4 Nanodelivery of NHC-platinum drugs 119 other proteins, while HSA usually binds a large amount of injected platinum, such phenomenon is not irreversible and slow platinum release has been reported. 287 Moreover, FDA approved the use of the biocompatible HSA for pharmaceutical applications as illustrated by Levemir, Victoza and Ozoralizumab drugs. 289 Therefore, taking advantage of the high affinity of platinum complexes for albumin, 288 its use as a biocompatible carrier has been suggested. 289,290 This strategy allowed improvement of drug stability and proved promising to treat brain tumours as an alternative to clinically used drugs which usually fail at crossing the blood-brain barrier. 291

Scheme 38: Structure of Pt(IV) complexes designed to selectively bind to albumin 287,292,293,294 Several Pt(IV) derivatives have been reported to bind to albumin by either covalent bonding of a maleimide moiety to the free thiol of Cys34 292,293 or non-covalent binding. 294,287 Such combination prevented side reactions at the metal centre 278 in addition to improve blood stability and cytotoxicity compared to free Pt(IV) complexes. 295 The authors therefore suggested that administration of the performed macromolecular drug is preferred. 287 Remarkably, the combination of a mono-functionalized maleimide containing platinum(IV) complex to HSA allowed successful mice recover thanks to both long time frames of disease stabilization and tumour inhibition by apoptosis. 293 However, all described Pt(IV) complexes covered with albumin follow the SAR rule, thus combination of NHC-Pt(IV) derivatives to albumin would be of interest for anticancer applications. UV spectroscopy is a common analysis technique to investigate protein structural changes and discover the formation of a protein-drug adduct. 296,297 Indeed, the UV spectrum of BSA displays overlapping bands with a maximum intensity at λ = 280 nm corresponding to the ππ* transitions of aromatic residues, namely tryptophan, tyrosine and phenylalanine. 298 Therefore, UV analysis of the macromolecules 109-112 with a 1Pt/1BSA ratio at a BSA concentration of 2.5x10 -6 M were carried in a 9/1 mixture of H2O/DMSO (Figure 32).

All macromolecules loaded with NHC-Pt drugs displayed an increase in their maximum of absorption, thus confirming an interaction between platinum complexes and the protein.

Moreover, both macromolecules 109 and 111 loaded with chlorine-platinum derivatives promote the most important absorbance increase in addition to blue shift (λBSA = 277 nm while λ111 = 269 nm). This seem to suggest a strong static interaction between the NHC-Pt derivative and aromatic moieties in the BSA. 299,300 Finally, no protein unfolding was observed by UV-vis measurement, thus suggesting that no BSA unfolding occur in the presence of NHC-Pt complexes. 301 To ensure efficient drug release, the mixture of BSA-Pt 110 was dialyzed over one litre of water for three days and dialysate was lyophilized and analysed by 1 H NMR. The spectra displayed identical resonance signals to the NHC-Pt(II) complex 2, thus confirming efficient release from the protein of the intact drug.

Finally, the efficiency of NHC-Pt combination to the albumin carrier at promoting anticancer activity has been explored by mean of IC50 measurements on both HCT116 and PC3 cancer cells and compared to cisplatin and free NHC-Pt complexes (Figure 33). Remarkably, the cytotoxicities displayed in Figure 33 proved to be highly dependent the nature of the halogen ligand at the platinum centre rather than the oxidation state of the metal.

3) Conclusion

In conclusion, the use of albumin as a carrier for NHC-Pt complexes has been investigated by varying both the nature of the halogen ligands at the metal and the platinum oxidation degree which proved to greatly influence drug stability. Moreover, the ratio of platinum complex per protein can be easily tuned and affords a large range of nanodelivery devices which proved stable in solution over a week. The efficient drug uptake was easily confirmed by UV-vis measurements which suggest NHC-Pt complexes to be located in the albumin hydrophobic pockets near tryptophan moieties. Finally, in vitro cytotoxicity investigation highlighted contrasting results between the nanodevices bearing chlorine derivatives of NHC-Pt complexes which failed at inducing cell death and both bromine macromolecules 109 and 111 which exerted moderate potencies. Accordingly, in vivo potency measurements would be necessary to investigate the gain of covering NHC-Pt complexes with albumin toward both the side effects decrease and cancer cell targeting.

II. Liposomal formulation

Liposomes are synthetic spherical vesicles composed of amphiphilic molecules which selfaggregate and form a phospholipid bilayer envelope. They are biocompatible and Chapter 4 Nanodelivery of NHC-platinum drugs 124 biodegradable, and offer the possibility to encapsulate either hydrophobic or sensitive drugs and deliver them to targeted cancer cells without promoting side effects. The easy variation of their physiological properties by modification of the lipid nature, size or particle charge raised considerable interest in the last decades, several liposomal formulations being already used in clinics. 302 Therefore, we synthesized NHC-Pt complex 48 functionalized with a lipophilic didecylamine to favour its incorporation into the anionic liposomes concomitantly to a mixture of phospholipids, namely phosphatidylcholine, phosphatiydylglycerol and cholesterol. The liposomal formulation using 5% of the [(NHC)PtI2(didecylamine)] complex 48 has been investigated in collaboration with Pr S. Fournel (Faculté de Pharmacie de Strasbourg). Selfaggregation into spherical liposomes of ~ 60-70 nm using the technique of lipid film hydration proved successful as confirmed by DLS measurements. Moreover, preliminary cytotoxicity experiments seem to suggest that NHC-platinum loaded liposomes promoted viability inhibition of HCT116 cancer cells over a complex concentration of 30 µM. Complementary investigation of the influence of drug loading ratio and comparison to the free drug are currently underway in order determine the optimal NHC-platinum loading and evaluate the possible gain in both stability and anticancer activity. In the end, the liposome loading with the [(NHC)PtBr4L] complex 90 would be evaluated in order to overcome stability issue and ultimately afford highly cytotoxic drug.

III. Biocompatible and water-soluble polycationic Pt(II)-NHC macromolecules

As emphasized in the introduction, numerous strategies have been developed in order to circumvent side effects associated with cisplatin-based chemotherapy. Among them, drug delivery based on polymeric assemblies has raised massive interest to protect the platinum centre from side reactions and to promote selective platinum accumulation to cancer cells through EPR effect. 303 Among them, polyethylenimine (PEI) is a well-established biocompatible polymer used as an efficient transfecting agent. 304 It can be obtained by straightforward synthesis based on either aziridine polymerization or acidic hydrolysis of functionalized oxazoline moieties. The potential of PEI to transfect DNA has first been highlighted by the group of Behr 305 and further extended to a wide number of biological material for gene delivery. 306 The peculiar proton-sponge ability of PEI resides in its network of protonable nitrogen atoms depending on the surrounding pH. Indeed, these amino groups have a pKa of 5.5 which easily allow formation of a polycationic system capable to condensate with DNA or other biological material by electrostatic interactions. In vivo, this polycationic macromolecule is expected to target cells thanks to electrostatic interaction with the negatively charged phospholipid cellular membrane. Drug delivery is believed to occur through cell endocytosis of the drug-PEI nanoparticle. Endosomal escape is favoured by the action of enzymes (ATPase) which acidify the media within the nanoparticle thus promoting PEI protonation and elongation. 307 Subsequent osmotic swelling provoke a rupture of the endosomal membrane and drug release into the cytoplasm (Figure 35). 308 A complementary in vitro analysis confirmed the potential of the 113 macromolecule which displayed higher potencies than the two clinically used cisplatin and oxaliplatin (Figure 37). Similar trends were observed in vivo on nude mice which were administered the 113 cytotoxic complex. Indeed, greater tumour volume control and lower side effects have been observed compared to mice treated with oxaliplatin which suffered haemorrhagic events (Figure 38).

Complementary in vivo work on immunocompetent mice confirmed the efficiency of NHC-Pt-PEI complexes at promoting high anticancer activity despite the possible immune response. This strategy proved efficient for various moieties and allowed easy and quantitative generation of diverse functionalized polymers. Adamantyl group is known to promote host-guest interaction with cyclodextrin rings and is thus of great interest for further post-functionalization, 310,311 in particular in the field of material dedicated to biological use. 312,313 Scheme 43: PEI based copolymers functionalized with hydrophilic and lipophilic polymers 117-121 respectively were obtained in quantitative yields after multiple centrifugations in diethyl ether (Scheme 47). While overlapping of most NHC characteristic protons with fluorescent aromatic moieties was observed in 1 H NMR, ligand exchange at the platinum centres could be ascertained thanks to the N-methyl protons found as a singlet at around 4 ppm. This characteristic signal was also used for quantification of the platinum amount actually grafted. To note, no luminescence decrease has been observed in solution after polymer functionalization with multiple platinum centres, and the coumarin functionalized complex 132 proved once more the most luminescent derivative and promising for further in vitro biodistribution investigation. However, drug functionalization with bulky chromophore might slightly modify its physicochemical properties and consequently both its biodistribution and fate. Therefore, these observations should be considered carefully and supported by complementary analysis such as colocalization study or ICP-MS measurement.

(
In order to determine whether the functionalization with chromophores modify the drug uptake, the combination of 113 with a different chromophore has been investigated and its in vitro distribution has been compared to the previously synthesized NHC-Pt-PEI-FITC derivative 133. We selected the epicocconone motif which is a natural compound intrinsically nonfluorescent. However, its intense red fluorescence after intermolecular ring-opening with amine groups (Scheme 49), and especially with proteins, raised it as a powerful staining agent in biological investigations under the brand name of Lavapurple. 314 The major asset of the epicocconone family is its huge stokes shift as exemplified by Lavapurple which λem = 610 nm is found almost a hundred nanometers above with λexc = 520 nm.

142 ppm and UV-vis spectrum displayed two absorption bands at 269 nm and 420 nm, characteristic of the epicocconone moiety. One intrinsic limitation in the use of epicocconone derivatives is their rapid photobleaching which has been previously reported to reach 83% fluorescence lost within 19 minutes 315 in addition to its pH dependent stability which maximum is pH 2.5. 316 The introduction of a chromophore on the NHC-platinum motif by strong covalent bond has been envisioned to follow NHC-Pt release from the PEI in vitro, and explore its biodistribution and compare with the fluorescent polymer 133. Moreover, the carbene-platinum bond is believed to be exceptionally stable toward biological media, thus marking the NHC ligand appeared as a straightforward method to follow the platinum fate in vitro without inducing major electronic and steric modifications at the metal centre.

Fluorescein binding through condensation of the 6-aminofluorescein on the aldehyde derivative 13 has been investigated according to previously reported procedure. 317 However, the complex 13 proved inert toward condensation even in presence of an excess of fluorescein (Scheme 51).

This lack of reactivity has previously been observed in our lab in the case of large and rigid molecules and might explain the failure of fluorescein condensation under mild conditions. precursor bearing an ethanol N-substituant developed in our group also failed and only starting materials could be recovered. 318 Therefore, chromophore conjugation onto the NHC ligand through click reaction has been investigated according to previously reported procedure (Scheme 52). 118 First reaction step This strategy successfully allowed the synthesis of a NHC-Pt-PEI conjugate with chromophore binding through the highly stable triazol-moiety which should allow successful in vitro monitoring of the platinum biodistribution and colocalization study with complexes 133 and 134.

In addition, the coordination of a non-metallated porphyrin-modified NHC-Pt moiety has been attempted by reacting in ethanol the precursor 23 using a 1Pt/30NH ratio similarly to the procedure described in scheme 40. However, despite a one week long reflux conversion remained uncomplete and only moderate amount of porphyrin-NHC-Pt-PEI conjugate 138 was isolated as confirmed by 1 H NMR and UV analysis (Scheme 53 and Figure 44). reported procedure. 323 The nucleophilic substitution on the N-succinimide moiety was ensured by 1 H NMR as pyridyl protons of 140 were observed over 7 ppm in the PEI protons free area.

Similarly, 13 C NMR displayed carbon resonance signals characteristic of pyridyl and carbonyl carbons visible around 120 ppm and 165 ppm respectively. functionalized with a targeting moiety HB-19 remains to be evaluated in vitro as anticancer agent and its efficiency at targeting surface overexpressed nucleoline will be the matter of future studies.

3) Conclusion

Various strategies have been developed to allow alternatively pre-or post-functionalization of the cytotoxic NHC-Pt-PEI conjugate in excellent yields. Successful chromophore grafting and platinum coordination have been confirmed by 1 H NMR for all derivatives presented herein and UV techniques supported the polymer functionalization with all chromophores envisioned. A convenient two steps synthesis has been developed to allow tuneable conjugation of sulphur containing targeting moieties such as HB-19 which is expected to improve drug uptake.

Moreover, while the PEI functionalization at both extremities appeared to prevent selforganization into vesicular systems, some selected examples proved to undergo comparable potencies as the highly cytotoxic complex 113 with a 1Pt/30NH ratio. Finally, preliminary in vitro investigations of the biodistribution of fluorescent metallopolymers supported the successful complex internalization which is of importance to promote efficient anticancer activity.

Complementary experiments are currently underway to determine whether the expected platinum release from the PEI indeed occurs and allows platinum entry into the nucleus to promote cell apoptosis via a DNA platination.

IV. Gold nanoparticles for the delivery of NHC-Pt

1) Gold nanoparticles for biomedical application

Encouraged by the great anticancer activities and negligible side effects observed both in vitro and in vivo for the NHC-Pt-PEI conjugates detailed above, their association with well-defined metal nanoparticles (NPs) appeared as a powerful strategy to upgrade these anticancer agents.

Gold nanoparticles (AuNPs) are of particular interest for biomedical applications thanks to their high stability and biocompatibility. 324 Moreover, two preparations based on PEG coated gold nanoparticles, namely AurImmune™ and AuroLase™ have already been through clinical trials and approved by the FDA. 325,326 The use of either branched or linear polyethylenimine with various molecular weights have already been investigated for purposes as transfecting agents, 327,328 chemiluminescence agents, 329 sensors and even contrast agents. 330,331 Several PEI coated gold nanoparticles successfully entered cell nucleus and proved promising as transfecting agent. 332 Therefore, the synthesis of PEI coated gold nanoparticles (PEI-AuNPs) as cargo and subsequent grafting of NHC-Pt moieties have been investigated to improve both drug uptake by passive diffusion and biocompatibility. Moreover, the combination of NHC-Pt-PEI to gold nanoparticles is expected to prevent side effects and allow further biodistribution study.

2) Synthesis and characterization of PEI coated gold nanoparticles

In the literature, numerous synthetic pathways have been reported to access gold nanoparticles stabilized by PEI, particularly direct synthesis by thermal reduction 332 using an additional reducing agent or by ligand exchange on gold nanoparticles previously synthesized according to

Turkevich's method. 333 Under the guidance of Dr J.-L. Gallani (IPCMS, Université de Strasbourg),

we developed two convenient procedures involving the spontaneous assembly of gold atoms by chloroauric reduction with tetrabutylammonium borane (TBAB) to form PEI-AuNPs with an average size diameter of 10.7 nm or 30.9 nm under mild conditions. To note, other reducing agents as sodium borohydride or ammonium citrate have been envisioned but further dismissed due to the large size polydispersity observed. Several parameters proved essential in the synthesis of well-defined spherical particles rather than amorphous objects, namely solvents, Remarkably, while 10 nm PEI-AuNPs proved moderately stable in PBS as slow aggregation could be seen over three days, no signal broadening or shift of the maximum absorption peak was observed in mice serum. This suggests a great colloidal stability in biological media. Moreover, 30 nm PEI-AuNPs also proved stable for days in both PBS solution and mice serum as suggested by UV-vis measurements. These results support the great stabilization of these AuNPs with the 154 PEI coating which contrasts with precedent reports suggesting linear PEI to form poorly stable conjugates with gold nanoparticles. Erreur ! Signet non défini.

While gold nanoparticles usually improve the pharmacokinetics and biodistribution of therapeutic molecules, their size and shape determine their in vitro and in vivo fate. Therefore, the cytotoxicity of both sizes of drug-free PEI-AuNPs developed in our laboratory has been evaluated toward three cancer cell lines by mean of IC50 measurements (Figure 47).

Interestingly, the potency profiles proved to be dependent on the nanoparticle size since smaller nanoparticles (~ 10 nm) were non-toxic even at doses up to 400 µM. Distinctively, larger nanoparticles of ~ 30 nm exhibited low cytotoxicity toward all cancer cell lines. This is coherent with previous reports highlighting the biocompatibility of small gold nanoparticles stabilized by PEI. 332,334 Moreover, PEI-AuNPs are known to localize preferentially to the cell nucleus and faster exocytosis of smaller NPs might also account for their improved biocompatibility. 335 These results confirmed the potential of PEI-AuNPs developed herein for use as a biocompatible cargo for further nanodelivery of the cytotoxic NHC-Pt complexes. Finally, the grafting of cytotoxic NHC-Pt moieties at the surface of the biocompatible PEI-AuNPs by ligand exchange has been attempted under numerous reaction conditions (temperature, solvent and reaction time). Unfortunately, all tested conditions either promoted an irreversible nanoparticles aggregation or failed at coordinating the platinum centre as confirmed by X-ray photoelectron spectroscopy (XPS). Accordingly, more development is needed to allow efficient grafting of NHC-Pt complexes at the surface of gold nanoparticles and the binding through a modified NHC backbone functionalized with thiol moiety might be a solution.

3) Conclusion

We successfully developed a reproducible synthetic strategy to access hydrophilic small gold nanoparticles stabilized by the biocompatible polyethylenimine. Interestingly, the PEI-AuNPs

General Conclusion

In this work, we reported on the synthesis of various platinum drug candidates functionalized with easily tuneable N-heterocyclic ligands to improve their stability and overcome resistance mechanism associated to platinum(II) based chemotherapy. We first envisioned the modification of platinum coordination sphere by simple ligand exchange for the development of a library of metallodrugs displaying promising anticancer activities.

Additionally, the upgrade of a large range of NHC-Pt(II) precursors also by simple oxidation using either bromine or PhICl2 oxidants has been investigated to access NHC-Pt(IV) prodrug candidates. Comprehensive examination of the stability, drug release efficiency and anticancer activity of novel NHC-Pt(IV) complexes highlighted them as tremendous alternatives to cisplatin like drugs. Moreover, the occurrence of a parallel mechanism of action involving mitochondrial death by generation of oxidative stress successfully provided great cytotoxicity toward resistant cancers.

Furthermore, with the aim to access water-soluble and selective anticancer agents with improved cellular uptake, the combination of cytotoxic NHC-platinum moieties to various nanodelivery devices has been investigated. The use of natural albumin as a cargo appeared as a straightforward approach to allow biocompatible formulation of NHC-platinum complexes though preliminary in vitro tests were varied and further comprehensive drug screening is needed. Furthermore, liposomal formulation of an amphiphilic NHC-platinum complex successfully allowed drug release to promote cancer cell death. We also reported on the development of a family of polycationic NHC-Pt-PEI conjugates easily functionalized in high yields by modular approaches which offered the possibility to conjugate chromophores or targeting peptide to further improve their selectivity and potency. These macromolecules proved highly efficient at promoting cancer cell death either in vitro or in vivo and their mechanism of action and biodistribution are currently being unravelled by support of fluorescence microscopy.

Finally, we developed an easy and reproducible synthesis of two sizes of PEI coated gold nanoparticles though their functionalization with NHC-platinum derivatives requires additional investigation.

Encouraging results were obtained in the development of high valent NHC-Pt(IV) complexes and the synthesis of [(NHC)PtCl4L] complexes based on oxidation using PhICl2 could be extended to more complex structures. Moreover, the access to dual action derivatives combining selected organic drugs could be of interest for synergistic cytotoxicity. Crystal data were collected at 173 K using MoKα graphite monochromated (λ = 0.71073 Å)

radiation on a Nonius KappaCCD diffractometer. The structures were solved using direct methods with SHELXS97552 and refined against F2 using the SHELXL97 software. Non-hydrogen atoms were refined anisotropically. Hydrogen atoms were generated according to stereochemistry and refined using a riding model in SHELXL97. Dynamic light scattering (DLS)

were performed on a VASCO γ from Cordouan Technologies.

2) Protocols of cell culture and proliferation assay

Cancer cell lines were obtained from the American Type Culture Collection (Rockville, MD, USA)

and cultured according to the supplier's instructions. Human HCT116 colorectal carcinoma, MCF7 breast adenocarcinoma and PC3 prostate adenocarcinoma cells were grown in RPMI 1640 supplemented with 10% fetal calf serum (FCS) and 1% glutamine. Cell lines were maintained at 37 °C under a humidified atmosphere containing 5% CO2. Cell growth inhibition was determined by an MTS assay according to the manufacturer's instructions (Promega, Madison, WI, USA).

Briefly, the cells were seeded into 96-well plates (2.5 × 103 cells per well) containing 200 μL of growth medium. After 24 h of culture, the cells were treated with the tested compounds at different final concentrations. After 72 h of incubation, 40 µl of resazurin was added for 2 h before recording the absorbance at 490 nm with a spectrophotometric plate reader. The IC50 corresponds to the concentration of the compound that induces a decrease of 50% in the absorbance of drug-treated cells compared with untreated cells. Experiments were performed in triplicate.

3) Synthesis of functionalized imidazolium salts

▪ Procedure A: Synthesis of [(NHC)PtX2(pyridine)] complexes

All imidazolium salts are obtained using standard synthesis procedures in 250 mg to 1 g scale by alkylation of azole derivatives with excess halogenoalkane in CH3CN overnight at 75 °C. After evaporation of the volatiles, the crude product is dissolved in a minimum amount of methanol, washed with diethyl ether and dried under reduced pressure to yield the imidazolium salt.

Synthesized according to procedure A. Yellow oil, yield 92%. 1 H NMR (CDCl3,300 MHz,20 °C) 22.6, 26.2, 29.0, 29.3, 29.5, 29.7, 30.3, 31.9 (CH2) 8, 127.8, 128.1, 128.6, 128.8, 129.1, 133.3, 134.3, 139.8, 142.2 (Car + Cim + NCHN), 180.8 (CHO).

Synthesized according to procedure A. White solid, yield 73%. 1 H NMR (CDCl3,300 MHz,20 °C): δ 4.17 (s, 6H, 2N-CH3), 7.21-7.36 (m, 6H, 2Hpyr, 4HAr), 7.7 (t, J=7 Hz, 1H, 1Hpyr), 9.07 (m, 2H, 2Hpyr); 13 C NMR (CDCl3, 75 MHz, 20 °C): δ 34.9 (N-CH3), 109.9 (CHAr), 122.9 (CHAr), 125.1 (CHpyr), 134.7

Synthesized according to reported procedure. 1 Red solid, 1 2, 129.4, 129.5, 129.6, 129.9 (CHar), 131.7 (Car), 131.9 (Car), 142.6

(NCHN), 143.7 (NCHN).

2) Synthesis of NHC-Pt(II) complexes

▪ Procedure B: Synthesis of [(NHC)PtX2(pyridine)] complexes

The ligand precursor (imidazolium halide, 1.1 equiv.), PtCl2 (1 equiv.), NaI (10 equiv.) and K2CO3 (10 equiv.) were suspended under argon in anhydrous pyridine (10 mL). The mixture was sonicated for 20 min, heated overnight at 100 °C, then concentrated under reduced pressure, dissolved in CH2Cl2, and filtered through a Celite plug. The residue was purified by silica gel chromatography (pentane/CH2Cl2, 1:1 to CH2Cl2) to afford the complex as a yellow powder. MHz, 20 °C): δ 4.09 (s, 3H, N-CH3), 5.82 (s, 2H, N-CH2), 6.63 (d, J=2.5 Hz, 1H, CHim), 6.82 (d, J=2.5 Hz, 1H, CHim), 7.31-7.39 (m, 5H, CHar), 7.46-7.50 (m, 2H, CHpyr), 7.75 (m, 1H, CHpyr), 9.03 (m, 2H, CHpyr); HMQC 1 H-195 Pt NMR (CDCl3, 64.2 MHz, 20 °C): δ -3304 (m). 22.7, 26.7, 29.2, 29.3, 29.5, 29.6, 29.7, 31.9 (CH2)

Synthesized

▪ Procedure C: Ligand exchange on NHC-Pt(II)-pyridine complexes

The [(NHC)PtI2(pyridine)] complex (10 mg, 1 equiv.) was reacted with the amine ligand (5 equiv.) in EtOH (2 mL) at 50 °C overnight. The resulting mixture was concentrated under reduced pressure, then dissolved in dichloromethane and subsequently precipitated by addition of pentane to afford the complex as light yellow powders in quantitative yield.

▪ Procedure D: Synthesis of Neutral NHC-Platinum-Pnictogen Complexes

A solution of the corresponding trans [(NHC)PtI2(pyr)] complex (1 equiv.) and the Pnictogen ligand (1.2 equiv.) in ethanol (1-5 mL) was stirred overnight at 55 °C, under argon atmosphere. 3 The crude mixture was then concentrated under reduced pressure and purified by silica gel chromatography (pentane/CH2Cl2, 1:1 to CH2Cl2) to afford the desired complex as a yellow solid.

51a. Synthesized according to procedure D. Yellow solid, 32.1 mg, yield 51%. 1 3.08, N 3.17; found C 38.92, H 3.17, N 3.43. 52a. Synthesized according to procedure with a slight modification. At the end of the reaction a pale-yellow precipitate was observed in solution. Ethanol was carefully removed with a syringe, and the yellowish precipitate was washed once with cold ethanol (0.5 mL) and dried under vacuum. Pure compound was obtained after silica gel chromatography (pentane/CH2Cl2, 20:80).

Yellow solid, 32.1 mg, yield 58%. 1 8, 123.2, 128.6, 129.4, 129.7, 130.9, 134.3, 134.9, 135.4 (Car), ) and DIPEA (1 equiv.) in ethanol (1-5 mL) was stirred overnight at 55 °C, under argon atmosphere. The crude mixture was then concentrated under reduced pressure and purified by silica gel chromatography (pentane/CH2Cl2, 1:1 to CH2Cl2) to afford the desired complex as a light yellow oil.

54.

Synthesized according to procedure E. Yellow solid, 10.4 mg, yield 31%. 1 H NMR (CDCl3,300 MHz, 20°C): δ 1. 30-1.87 (m, 54 H, nBu), 3.94 (s, 3 H, N-CH3), 5.39 (s, 2 H, N-CH2), 7.12 (s, 1 H, 196 CHim), 7.15-7.18 (m, 2 H, HAr), 7.40-7.43 (m, 3 H, HAr) 8, 14.3, 22.8, 24.3, 24.4, 24.5, 24.7, 27.0, 29.8, 30.5, 32.1, 39

▪ Procedure G: Direct oxidation with bromine

In a 10 mL round bottom flask, the precursor [(NHC)PtI2L]4 (10 mg, 1 equiv.) was dissolved in CH2Cl2 (5 mL) and cooled at 0 °C and Br2 (2 equiv.) was slowly added under nitrogen. After 30 min, pentane (10 mL) was added and the resulting red precipitate [(NHC)PtBr4L] was filtered off, washed and dried.

58.

Synthesized according to procedure G. Red solid, 13.1 mg, yield 99%. 1 (CHim), 129.2 (Car), 139.6 (Car), 143.5 (Car), 147.8 (Car), 147.8 (Cpyr), 154.4 (Cpyr); the carbene resonance peak was not observed; HMQC 1 H-195 Pt NMR (CDCl3, 64.2 MHz, 20 °C): δ -2067 ppm

68.

Synthesized according to procedure G. Red solid, 12.1 mg, yield 99%. 1 H NMR (CDCl3,300 MHz, 20 °C): δ 4.73 (s, 3H, N-CH3), 6.63 (s, 2H, N-CH2), 6.94 (d, J=8.3 Hz, 1H, Har), 7.18 (t, J=7.8 Hz, 1H, Har), 7.34 (m, 3H, Har), 7.46 (t, J=7.1 Hz, 2H, Hpyr), 7.57 (d, J=8.3 Hz, 1H, Har), 7.80 (d, J=8.3 Hz, 2H, Har), 7.89-7.94 (tt, J=7.6 Hz, 1H, Hpyr), 9.66-9.75 (q, J=16.5 Hz et J=10.7 Hz, 2H, Hpyr), 9.97 (s, 1H, CHO); 13 C NMR (CDCl3, 75 MHz, 20°C): δ 41.3 (N-CH3), 57.2 (N-CH2), 111.9 (N-Cim), 113.2

(N-Cim), 124.7 (t, J=9.8 Hz),125.1, 125.3, 127.4, 129.8, 133.9 (C-Pt), 135.6, 139.5, 143.1, 154.5, 191.5 (CHO).

69.

Synthesized according to procedure G. Red solid, 10.8 mg, yield 99%. 1 H NMR (CDCl3,300 MHz, 20 °C): δ 6.25 (bs, 4H, N-CH2), 6.73-6.75 (m, 4H, Har), 6.81 (m, 4H, Har), 6.99 (m, 4H, Har), 7.10-7.12 (m, 8H, Har), 7.46 (m, 2H, Hpyr), 7.91 (m, 1H, Hpyr), 9.75 (m, 2H, Hpyr); No 13 C NMR could be recorded due to low solubility. 1 H-13 C HMBC NMR (CDCl3, 500 MHz, 20 °C). d, J=10.4 Hz, 2Cim), 139.8 (Cpyr), 154.7 (s + d, J=4.6 Hz, Cpyr); HMQC 1 H-195 Pt NMR (CDCl3, 64.2

73.

Synthesized according to procedure G. Red solid, 12.7 mg, yield 99%. 1 H NMR (CDCl3,MHz,20 °C): δ 4.69 (s, 3H, N-CH3), 7.60 (s, 2H, CHim); HMQC 1 H-195 Pt NMR (CDCl3, 64.2 MHz, °C): δ -2071 (m). Insoluble.

74.

Synthesized according to procedure G. Red solid, 12.1 mg, yield 99%. 1 Car), 129.5 (Car), 134.7 (Car), 135.6 (Car), 139.9 (Car), 145.0 (Cpyr), 154.7 (Cpyr).

75.

Synthesized according to procedure G. Red solid, mg, yield 99%. 1 H NMR (CDCl3, 300 MHz, °C): δ 4.47 (s, 6H, N-CH3), 6.11 (s, 4H, N-CH2), 6.85 (s, 4H, CHim), 7.39-7.51 (m, 8H, CHar+CHpyr), 7.90 (m, 2H, CHpyr), 9.69 (m, 4H, CHpyr).

5) General procedure for reduction of [(NHC)PtX4(pyridine)] complexes in DMSO

The stability of the complexes was monitored in d6-DMSO by 1

7) Electrochemical investigation by cyclic voltammetry

All the electrochemical measurements were performed in a three-electrode cell using a 3 mm diameter glassy carbon disk working electrode and Pt electrodes as counter electrode and pseudo-reference electrode. To avoid the presence of dissolved oxygen, the solutions were purged with argon before each current-potential curve measurement. The voltammograms discussed in this work were acquired at a scan rate of 100 mV.s -1 at room temperature. The current-potential curves displayed in this have been obtained in the presence of a small amount of ferrocene, the origin of the potential axis being referred to the reversible redox waves of the ferrocene.

▪ Cyclic voltammetry of NHC-Pt(II) and NHC-Pt(IV) complexes in CH3CN

In this case, the platinum complex was added to a 5 mL acetonitrile solution ([Pt]~0.1 mM) containing 0.1 M TBAPF6 as supporting electrolyte. The current-potential curves were first measured in the absence and then in the presence of a small amount of ferrocene added for the potential axis calibration. 114. The procedure L was adapted using 10.1 mg of complex 5 and 25 mg of PEI to afford 114.

White muggy solid, quant. 1 H NMR (MeOD,500 MHz,20 °C) (m, CHim), 6.79 (m, CHim), 7.21-7.62 (m, 94H, CHim+Har); 13 C NMR (MeOD, 125MHz, 20 °C): δ 10. 1-10.7, 15.5, 18.4, 23.8, 24.5, 27.4, 29.9-30.8, 32.3, 33.2, 35.3, 38.4-43.0, 45.3-48.1, 50.9-53.3, 55.0-55.7, 56.6-58.1, 58.3, 59.8-60.9, 64.9, 67.0, 77.7, 79.1, 82.4, 119.1 (CHim), 124.2-125.1 (CHim), 129.6-130.8 (CHar), 131.4 (CHar), 135.6 (Car), 138.0 (Car).

115. The procedure L was adapted using 8.1 mg of complex 5 and 25 mg of PEI to afford 115.

White muggy solid, quant. 1 10.5,14.5, 19.9, 23.7, 24.3, 27.2, 28.1, 29.9-30.8, 33.1, 35.3, 36.6, 46.3-48.0, 52.5-57.0, 59.9, 79.0-79.6, 119.1 (CHim), 124.3-124.9 (CHim), 129.6-130.6 (CHar), 131.3 (CHar), 135.7 (Car), 138.3 (Car).

116. The procedure L was adapted using 4 mg of complex 5 and 25 mg of PEI to afford 116.

White muggy solid, quant. 1 (m, CHim), 6.80 (m, CHim), 6.95-8.45 (m, 94H, CHim+Har); 144 Synthesized according to procedure L. Light yellow oil, quant. 1 in water is slowly added to the mixture and vigorously stirred for one hour at 50°C until appearance of the characteristic dark red colour. The reaction mixture is then purified by dialysis over 500 mL of water using a 10 kDa cut-off membrane for 24 h and obtained as a stable dark red solution in water.

▪

▪ Synthesis of 30 nm PEI-AuNPs

To a solution of HAuCl4.6H20 (25 mg, 0.73 mmol, CAu = 6.4 mM) in water is added 0.02 equivalents of PEI and stirred for 30 minutes at 20°C. Then, a solution of TBAB (0.1 equivalents) in water is slowly added to the mixture and vigorously stirred for 20 minutes at 20°C until appearance of the characteristic dark red colour. The reaction mixture is then purified by dialysis over 500 mL of water using a 10 kDa cut-off membrane for 24 h and obtained as a stable dark red solution in water.

▪ UV-vis analysis of selected batch

  Damien et Michel pour leur présence au labo. Merci également à Melania/Carotte, Matthieu & Sonia & Heather, Anis, Catalina, Mimi V. & Christophe, Dédé, Senthil, Sébastien P., Janah, Sébastien K. pour les bons moments passés ensemble. Je tiens également à remercier l'ensemble des membres du DMO pour leur bonne humeur permanente. Merci particulièrement à Nico qui a toujours été là pour aider à résoudre n'importe quel problème technique. Mention spéciale pour Bertrand qui m'a prodigué de nombreux conseils pour mon envol vers Philly. Merci à l'équipe des TPs inorga et particulièrement à Vincent pour ses conseils avisés. Je veux également remercier Woody ainsi que Dominique qui m'ont soutenue et m'ont donné gout à la recherche. Finalement, un énorme merci à mes Grands-Parents, Monique et Alain, pour leur appui et particulièrement à ma Mère, Christine, pour son soutien en toute circonstance et grâce à qui cet objectif a pu devenir une réalité. Je tiens également à remercier ma belle-famille pour leur aide et leur gentillesse constante. Enfin, merci à Niels qui a toujours été présent pour m'encourager et me tirer vers l'avant.

1 )

 1 Abbreviations

1 ) 10 Publications 1 ) 2 )

 11012 Stability of NHC-Pt(IV) complexes in organic solvent and mice serum 2) Investigation of the NHC-Pt(IV) reduction process by biological reducing agent 3) Electrochemical investigations III. Anticancer activity and mechanism of action of NHC-Pt(IV) prodrugs 1) Cytotoxicity of selected NHC-Pt(IV) prodrug candidates 2) Efficiency of NHC-Pt(IV) complexes toward cisplatin resistant cell lines 3) Binding experiments 4) Mitochondria as an alternative target: from ROS generation to mitochondria dependent cytotoxic pathway IV. Conclusion Chapter 4: Nanodelivery of NHC-platinum complexes I. Proteins as biocompatible carrier 1) State of the art: albumin in drug delivery 2) NHC-Pt(IV) uptake by bovine serum albumin 3) Conclusion II. Liposomal formulation III. Biocompatible and water-soluble polycationic Pt(II)-NHC macromolecules 1) Background in the development of PEI-platinum conjugates within our group 2) Diversity enhancement by functionalization of NHC-Pt-PEI conjugates 3) Conclusion IV. Gold nanoparticles for the delivery of NHC-Pt 1) Gold nanoparticles for biomedical application 2) Synthesis and characterization of PEI coated gold nanoparticles 3M. Bouché, G. Dahm, A. Maisse-François, T. Achard, S. Bellemin-Laponnaz « Selective Formation of cis-N-Heterocyclic Carbene-Pt II -Pnictogen Complexes and in vitro Evalutaion of Their Cytotoxic Activities toward Cancer Cell s» Eur. J. Inorg. 2016, 2828-2836 M. Bouché, G. Dahm, M. Wantz, S. Fournel, T. Achard, S. Bellemin-Laponnaz « Platinum(IV) N-heterocyclic carbene complexes: their synthesis, characterization and cytotoxic activity »Dalton Trans. 2016, 45, 11362-11368

Figure 1 :

 1 Figure 1: Structure moléculaire d'un complexe neutre d'arsenic 52b (gauche) et d'un complexe d'antimoine 51c (droite).

Figure 2 :

 2 Figure 2: Structures moléculaires de deux complexes de type [(NHC)PtBr4(pyridine)] 77 (A) et 81 (B).

  H, confirmant ainsi la formation d'une nouvelle espèce où le centre métallique est réduit au degré d'oxydation +II et la pyridine a été substituée par une molécule de DMSO. Pourtant, il est apparu que la cinétique de cette réaction est dépendante du potentiel redox des complexes puisque les dérivés [(NHC)PtBr4L] réagissent en moins de 24h alors que la famille [(NHC)PtCl4L] a montré une bonne stabilité sur plusieurs mois, montrant clairement leur plus grand intérêt pour des études biologiques. Ceci a pu être confirmé par voltamétrie cyclique et a souligné l'importance de la quantité d'eau présente dans la solution de DMSO sur la cinétique de cette réaction.

Figure 3 :

 3 Figure 3: Tendances générales observées pour la conversion des complexes NHC-Pt(IV)-amine en une nouvelle espèce NHC-Pt(II)-DMSO en fonction du temps dans un mélange DMSO/H2O

Figure 4 :

 4 Figure 4: Evolution par voltammétrie cyclique à 100 mV.s -1 d'un complexe [(NHC)PtCl4(pyridine)] dans une solution de DMSO et 0,1 M de TBAPF6 en présence d'un équivalent de GSH

Figure 5 :

 5 Figure 5: Evaluation de l'interaction des complexes NHC-Pt(II) 2, 4 ainsi que des complexes NHC-Pt(IV) 59, 95 avec l'albumine par spectroscopie UV-vis (ratio de 1Pt/1BSA)

Figure 6 :

 6 Figure 6: Vue de cellules cancéreuses traitées avec le complexe 133 par épifluorescence sous A) lumière blanche, B) lumière UV à λ = 365 nm

Figure 7 :

 7 Figure 7: Images typiques obtenues par microscopie électronique en transmission sur un échantillon de PEI-AuNPs avec un diamètre moyen de 10 nm

Figure 8 :

 8 Figure 8: Platinum-DNA adduct structures. Duplex DNA containing (A) cisplatin 1,2-d(GpG), (B) 1,3d(GpTpG) intrastrand, and (C) cross-links, generated by PyMol. 21

Figure 9 :

 9 Figure 9: General cell cycle graph

  and subsequent inhibition of the RNA transcription process.45 Finally, caspases 3 and 7 enzymes which are responsible for polypeptidic chains cleavage have been largely accepted as being involved in the cisplatin induced apoptosis thus supporting DNA fragmentation.46

Figure 10 :Figure 11 :

 1011 Figure 10: Pathways for cisplatin-induced apoptosis and necrosis

Scheme 4 :

 4 Scheme 4: Most common backbones of free NHCs

Scheme 7 :

 7 Scheme 7: Selected examples of potent drugs synthesized by post-functionalization strategies

Scheme 8 :

 8 Scheme 8: Structure of platinum(IV) complexes which entered clinical trials

Scheme 13 :

 13 Scheme 13: General synthesis of NHC-Pt(II) precursors (X = Cl, Br, I)

Scheme 18 :

 18 Scheme 18: Complex architectures based on a) homo-bimetallic NHC-Pt(II) precursors, b) non-Nheterocyclic carbenes-Pt(II) complexes

  molecular structure of several [(NHC)PtI2(pyridine)] complexes could be determined by Xray diffraction; some selected examples are presented in Figure 5. All NHC-Pt(II)-pyridine complexes display specific features as a trans configuration of the coordinated pyridine to the NHC ligand with the expected square planar geometry at the platinum centre. Both iodide ligands are facing each other in a trans configuration and point perpendicularly toward the NHC ligand plane. This possibly indicates interactions between the lone pairs of electrons on the iodide ligands and the formally antibonding p orbital of the NHC carbon atom. This is supported by the interatomic distances CNHC•••I with both iodides of ~ 3.25 Å compared to the sum of the van der Waals raddi for both carbon iodide (~ 3.68 Å).

Figure 12 :

 12 Figure 12: Structure of selected trans [(NHC)PtI2(pyr)] complex 5, 13 and 15. 125 Selected bond distances [Å] and angles [°]: 5 Pt(1)-C(1), 1.974(7); Pt(1)-N(3), 2.094(6); Pt(1)-I(1), 2.5934(5); Pt(1)-I(2), 2.6025(5); C(1)-Pt(1)-I(1), 89.4(2); N(3)-Pt(1)-I(2), 90.4(2); I(1)-Pt(1)-I(2), 178.40(2); 13 Pt(1)-C(1), 1.981(6); Pt(1)-N(3), 2.091(4); Pt(1)-I(1), 2.5918(4); Pt(1)-I(2), 2.6031(4); C(1)-Pt(1)-I(1), 88.58(15); N(3)-Pt(1)-I(2), 90.50(12); I(1)-Pt(1)-I(2), 176.944(16); 15 Pt(1)-C(1), 1.961(4); Pt(1)-N(3), 2.088(3); Pt(1)-I(1), 2.5732(3); Pt(1)-I(2), 2.6013(3); C(1)-Pt(1)-I(1), 87.72(10); N(3)-Pt(1)-I(2),91.76(9); I(1)-Pt(1)-I(2), 172.401(14).

61 2 )

 2 Scheme 19: Lipophilic NHC-Pt(II) precursors obtained by ligand exchange

Figure 13 :

 13 Figure 13: LogP values for selected compounds

Scheme 20 :

 20 Scheme 20: Pyridine substitution on NHC-Pt(II) precursors with PPh3, AsPh3, or SbPh3

Figure 14 :

 14 Figure 14: Molecular structure of selected arsine and antimony neutral complexes 52b (left) and 51c (right). Selected bond lengths [Å] and angles [°]: 52b Pt(1)-C(1), 1.991(6); Pt(1)-I(1), 2.6263(5); Pt(1)-I(2), 2.6488(4); Pt(1)-As, 2.3551(6); C(1)-Pt(1)-I(2), 175.46(16); As(1)-Pt(1)-I(1), 179.75(2); 51c Pt(1)-C(1), 1.983(9); Pt(1)-I(1), 2.6490(7); Pt(1)-I(2), 2.6374(6); Pt(1)-Sb(1), 2.5066(6); C(1)-Pt(1)-I(2), 176.8(2); Sb(1)-Pt(1)-I(1), 169.56(2).

  ) Å. Moreover, no significant carbene-platinum bond length change is observed when varying the NHC backbone ca. 1.99 Å, thus underlying a minor influence toward the electron density at the metal centre. Interestingly, in the solid state, both arsine and stibine complexes bearing the anthracene moiety are stabilized by a CH-π intramolecular bond (3.055 Å) with a phenyl ring on the pnictogen. Similar behaviour appeared in the case of the benzimidazolin-2-ylidene Pt series where a CH-π intramolecular bond of 3.69 Å was found between the two ligands, namely the pnictogen phenyl ring and the NHC backbone.

Scheme 21 :

 21 Scheme 21: Phosphonium pathway to access NHC-Pt-phosphine complexes 54 and 55

Figure 15 :

 15 Figure 15: Molecular structure of the cis intermediate of 55. Selected bond lengths [Å] and angles [°]: Pt(1)-C(1), 1.965(9); Pt(1)-I(1), 2.668(7); Pt(1)-I(2), 2.6589(8); Pt(1)-P(1), 2.253(2); H(24A)-N(2), 2.651; H(24B)-N(1), 3.004; C(1)-Pt(1)-I(2), 176.8(3); P(1)-Pt(1)-I(1), 175.39(6).

Figure 16 :

 16 Figure 16: Molecular structure of cationic complex 57a

Figure 17 :

 17 Figure 17: Half inhibitory concentrations (IC50 in μM) of the selected compounds against a range of human cell lines 200

Scheme 23 :Scheme 24 :

 2324 Scheme 23: Selective synthesis of trans [(NHC)PtBr4(pyridine)] complexes

Scheme 25 :Scheme 26 :Figure 18 :

 252618 Scheme 25: Structural modification on the carbene backbone on platinum(IV) derivatives

  Scheme 28: Lipophilic NHC-Pt(IV) complexes obtained by direct oxidation of [(NHC)PtI2L] complexes with L = primary or secondary amine ligand (99% yield in all cases)

Figure 19 :

 19 Figure 19: Molecular structures of moderately lipophilic [(NHC)PtBr4(pyridine)] complexes 77 (A) and 81 (B). Selected bond distances [Å] and angles [°]: 77 C(1)-Pt(1), 2.036(7); Br(1)-Pt(1), 2.4793(9); Br(2)-Pt(1), 2.4693(9); Br(3)-Pt(1), 2.4716(9); Br(4)-Pt, 2.4743(9); N(3)-Pt(1), 2.138(6); C(1)-Pt(1)-N(3), 175.7(3); C(1)-Pt(1)-Br(3), 95.0(2); N(3)-Pt(1)-Br(3), 88.3(2); Br(1)-Pt(1)-Br(3), 172.55(3); Br(1)-Pt(1)-Br(4),93.99(3). 81 C(1)-Pt(1), 2.074(13); Br(1)-Pt(1), 2.4754(18); Br(2)-Pt(1), 2.4748(15); Br(3)-Pt(1), 2.4770(18); Br(4)-Pt, 2.4748(17); N(3)-Pt(1), 2.167(12); C(1)-Pt(1)-N(3), 175.1(5); C(1)-Pt(1)-Br(2), 92.0(4); N(3)-Pt(1)-Br(3), 85.9(4); Br(1)-Pt(1)-Br(3), 176.46(6); Br(1)-Pt(1)-Br(2),93.47(6).

Scheme 29 :

 29 Scheme 29: Hypervalent iodine-mediated oxidation of Pt(II) precursors in [(NHC)PtCl4(pyridine)] complexes

Scheme 30 :

 30 Scheme 30: Successfully synthesized [(NHC)PtCl4(pyridine)] complexes(92-99% yield)

Figure 20 :

 20 Figure 20: Molecular structure of [(NHC)PtCl4(pyridine)] complex 94. Selected bond distances [Å] and angles [°]: C(1)-Pt(1), 2.034(11); Cl(1)-Pt(1), 2.329(3); Cl(2)-Pt(1), 2.327(3); Cl(3)-Pt(1), 2.336(3); Cl(4)-Pt, 2.330(3); N(3)-Pt(1), 2.127(9); C(1)-Pt(1)-N(3), 178.4(4); C(1)-Pt(1)-Cl(2), 91.6(4); N(3)-Pt(1)-Cl(2), 89.2(3); Cl(2)-Pt(1)-Cl(4), 177.34(12); Cl(1)-Pt(1)-Cl(4),91.85(12).

Scheme 34 :

 34 Scheme 34: Unsuccessful attempted oxidative addition at the platinum centre

Figure 21 :

 21 Figure 21: Selected examples of 1 H-195 Pt NMR spectra of 95 (above) and 6 (below) highlighting the proton coupling in long range with the platinum centre. Observed signals in ppm (CDCl3): 95 4.35 (N-CH3), 4.70 (N-CH2), 4.75 (N-CH2), 7.0 (CHim), 7.10 (CHim), 7.50 (CHpyr), 7,55 (CHpyr); 5 3.9 (N-CH3).

Figure 22 :

 22 Figure 22: Platinum shift of various NHC-Pt complexes in 195 Pt NMR (in CDCl3)

Figure 23 :

 23 Figure 23: Reaction progress with platinum complex 95 at 20°C in d-6DMSO over 70 days

Figure 24 :

 24 Figure 24: General trends observed in the conversion percentages of NHC-Pt(IV)-amine complexes into NHC-Pt(II)-DMSO as a function of time in a DMSO/H2O mixture

Figure 25 :

 25 Figure 25: Proposed mechanism of action for Pt(IV) prodrugs

Figure 26 :Scheme 36 :

 2636 Figure 26: Reduction of 95 by methionine in DMSO solution (10 -3 M, 20°C)

  of Pt(IV) complexes is highly dependent on the redox properties of the Pt(IV)/Pt(II) couple. Indeed, when the Pt(IV) reduction potential is shifted toward negative values, the active Pt(II) species release is slow, resulting in lower cytotoxicity. On the other hand, an increase of the Pt(IV) reduction potential will promote early drug release, thus allowing metalloproteinmediated deactivation. Reduction potentials EPt(IV)/Pt(II) of both NHC-Pt(IV) complexes and the oxidation of their Pt(II) precursor were investigated by cyclic voltammetry (CV). The experiments were performed in a regular three-electrode cell using a glassy carbon working electrode and Pt electrodes as counter electrode and pseudo-reference electrode in acetonitrile solution containing 0.1 M TBAPF6 as supporting electrolyte (Figure20). All experiments were performed at room temperature.In the following, the potential axes are referred to the ferrocenium/ferrocene redox potential as recommended by IUPAC when working in organic solvents.

Figure 20 presents

 20 Figure 20 presents voltammograms obtained at a scan rate of 100 mV.s -1 for [(NHC)PtX4(pyridine)] complexes with X = Br or Cl as well as [(NHC)PtX2(pyridine)] complexes with X = I, Br or Cl. To note, the synthesis of [(NHC)PtI4(pyridine)] complex met with failure and thus investigation remained restricted to NHC-Pt(IV) complexes 59 and 95. NHC-Pt(IV) complexes undergo a two-electron metal-centered reduction during the cathodic potential scan as exemplified by 59 where the reduction potential is Ered = -0.55 V. It should be mentioned that the halide ligands released during NHC-Pt(IV) reduction are oxidized at lower potential than the one of the NHC-Pt(II) reoxidation (Figure 20B), making the NHC-Pt(II) reoxidation wave difficult

Figure 27 :Figure 28 :

 2728 Figure 27: Cyclic voltammetry in 0.1 M TBAPF6 and acetonitrile solution at a scan rate of 100 mV.s -1 on A) NHC-Pt(IV) complexes 59 and 95, B) NHC-Pt(II) complexes 2, 4 and 6

Figure 29 :

 29 Figure 29: Cyclic voltammetry on both bromine and chlorine NHC-Pt(IV) complexes 59 and 95 respectively in DMSO at a scan rate of mV.s -1

Figure 30 :

 30 Figure 30: Cyclic voltammetry on bromine NHC-Pt(IV) complex 59 at a scan rate of 100 mV.s -1 in a 0.1 M TBAPF6 solution of a) DMSO, b) 95%DMSO/5%H2O, c) 85%DMSO/15%H2O, d) 76%DMSO/24%H2O

Figure 31 :

 31 Figure 31: Evolution complex 59 in a DMSO solution with 0.1 M TBAPF6 in the presence of one equivalent of GSH by cyclic voltammetry at 100 mV.s -1

Figure 32 :

 32 Figure 32: Half inhibitory concentrations IC50 (in µM) of selected compounds toward colon cancer cell HCT116, breast carcinoma MCF7 and prostate adenocarcinoma PC3

Figure 33 :Fresh

 33 Figure 33: Influence of stock solution preparation toward half inhibitory concentrations on 5

  regular and mutated cancer cells which developed acquired resistance to cisplatin based chemotherapy by inactivation of caspase-3 dependent apoptosis pathways (A2780 and A2780R respectively). To note, the capsase-3 has been proposed to be responsible for cleavage of the DNA fragmentation factor (DFF), thus activating apoptosis factors.

Figure 34 :Chapter 3

 343 Figure 34: IC50 measurement for 95 compared to cisplatin 246 toward A2780 and A2780R cell lines

Figure 35 :

 35 Figure 35: Evaluation of apoptosis on HCT116 p53 KO cell lines after treatment with 95, 59 or oxaliplatin at indicated concentrations (24 h of incubation). After treatment, cells were labelled Annexin V-APC and Propidium Iodide and analysed by flow cytometry. Significant flow cytometry dot plots showing apoptosis induction are represented. The percentage of early apoptotic cells (Annexin V + /PI -) and late apoptotic cells (Annexin V + /PI + ) are indicated.

  difference between free nucleobase and DNA chain in vivo. To gain more knowledge into the binding affinity of NHC-Pt complexes, complementary investigation on their reactivity toward DNS should be considered. Moreover, at the moment selected [(NHC)PtI2(pyridine)] drugs are under investigation in collaboration with Dr S. Harlepp (Institut de Physique et Chimie des Matériaux de Strasbourg) to evidence the formation of Pt-DNA adducts using optical tweezers.

Figure 36 :

 36 Figure 36: ROS production after cells treatment with selected compounds

  enzymes act as guardian for the redox homeostasis and usually restore the intracellular redox balance, therefore a secondary experiment has been performed using the same compounds to ensure their efficiency at overwhelming the antioxidant system and induce cell death. Similarly to the previous experiments, cells have been treated with the selected compounds and exposed to MitoTracker which is a dye that labels mitochondria within living cells based on the mitochondrial membrane potential, thus allowing differentiation between the populations of live and dead mitochondria.271

Figure 37 :Chapter 3

 373 Figure 37: Mitochondria respiration activity after cells treatment with selected compounds (C = 100 µM)

Figure 38 :

 38 Figure 38: Structure of the human serum albumin complexed with cisplatin 282

Chapter 4

 4 Scheme 39: General structure of NHC-Pt-BSA macromolecules 109-112 synthesized in various Pt/BSA ratio (5/1, 2/1, 1/1, 1/2, 1/5)

Figure 39 :

 39 Figure 39: Evaluation of the interaction of NHC-Pt(II) complexes 2, 4 and NHC-Pt(II) complexes 59, 95 with BSA by UV (1Pt/1BSA ratio)

Figure 40 :

 40 Figure 40: IC50 values of NHC-Pt-albumin macromolecules 109-112 toward HCT116 and PC3 human cancer (IC50 expressed in µM)

Chapter 4

 4 Indeed, while both macromolecules 109 and 111 bearing bromine ligands displayed moderate Nanodelivery of NHC-platinum drugs 123 activities toward both cancer lines (IC50 of ~ 16 µM), the macromolecules 110 and 112 proved inefficient at promoting cancer cell death. The encapsulation of NHC-Pt compounds into the albumin did not improve cytotoxicity compared to free drugs. Finally, no variation was observed in the potencies displayed by the Pt(IV) macromolecule 111 and its Pt(II) analogue 109 which tends to suggest that prodrug 59 reduction occurs when wrapped into the protein within the time scale of in vitro experiment.

Figure 41 :

 41 Figure 41: Viability percentage of HCT116 cancer cell lines treated with drug free liposome (blue), liposome loaded with 5% of NHC-Pt complex 48 (green)

Figure 42 : 1 )

 421 Figure 42: Gene delivery principle using polyethylenimine as transfecting agent

Figure 43 :

 43 Figure 43: Cryo-EM observation of free PEI and 113 309

Figure 44 :

 44 Figure 44: Cell viability on HCT116 treated alternatively with oxaliplatin, cisplatin and 113 309

Figure 45 :Figure 46 :

 4546 Figure 45: Antitumor effect on nude mice bearing HCT116 xenografts of 113 and oxaliplatin injected in vehicle at 5 µmol/kg 309

2 )

 2 Scheme 41: Three NHC-Pt-PEI conjugates with low platinum loading (quantitative yield)

Figure 47 :

 47 Figure 47: Percentage of cell inhibition of a HCT116 cancer cell line depending on the platinum loading on the polymeric chain

Scheme 42 :

 42 Scheme 42: General synthesis for amide formation on polyethylenimine

Scheme 44 :

 44 Scheme 44: Luminescent functionalized PEI derivatives (quantitative yields)

Scheme 47 :

 47 Scheme 47: Luminescent NHC-Pt-PEI conjugates obtained in quantitative yields

Figure 48 :

 48 Figure 48: Spectra comparison between free fluorescein and NHC-Pt-PEI conjugate 133 by A) UV-vis spectra, B) fluorescence analysis at λexc= 495 nm (C = 5x10 -6 M in ethanol)

Figure 49 :

 49 Figure 49: View of cancer cells treated with 133 by epifluorescence microscopy under A) white light, B) UV light at λ = 365 nm

Figure 50 :

 50 Figure 50: Viability percentages determined on HCT116 cancer cell line after treatment with 113 (green), 133 (orange) or 134 (red)

Scheme 51 :

 51 Scheme 51: Attempted synthesis of fluorescein condensation with the aldehyde derivative 13

Chapter 4

 4 Scheme 52: Functionalization of the NHC-platinum complex 135 with fluorescent coumarin derivative by click reaction and subsequent quantitative ligand exchange of 136 with PEI to afford 137

Scheme 53 :

 53 Scheme 53: Coordination of a NHC-Pt precursor 23 bearing a porphyrin modified NHC backbone to PEI

Scheme 56 :

 56 Scheme 56: Thiol exchange with GSH on the activated SPDP-PEI macromolecule 140

  concentration and the amount of reducing agent. After optimization process, the formation of an intermediate specie by reaction of 0.02 equivalent of PEI with one equivalent of HAuCl3 in water (CAu = 6.4 mM) at 20 °C proved essential. Subsequent slow reduction with 0.001 equivalent of TBAB for one hour at 50 °C promoted the successful formation of monodisperse PEI-AuNPs. The visual evolution from brown to deep red is characteristic for the arrangement of dispersed gold aggregates into spherical NPs (Figure45). Dialysis purification over 500 mL of water with a 10k Da cut-off membrane allowed isolation of pure PEI-AuNPs after 24 h. To note, storage was restricted to water solution at 20 °C due to irreversible aggregation when lyophilized or stored at lower temperature. This procedure allowed the synthesis of PEI-AuNPs with an average size of ~ 10 nm in a reproducible manner and which proved stable for weeks. A second procedure has been developed to access larger PEI-AuNPs of ~ 30 nm diameter. Chloric acid reaction in water with 0.02 equivalent of PEI for 15 minutes prior to rapid addition of larger amount of TBAB up to 0.1 equivalent promoted the formation of spherical nanoparticles after 15 additional minutes at 20 °C. Subsequent dialysis over water proved necessary to remove unreacted reducing agent and prevent the formation of amorphous or discoidal particles.

Figure 52 :

 52 Figure 52: Follow-up of the ~10 nm PEI-AuNPs synthesis by UV

Figure 53 :

 53 Figure 53: Typical TEM images of synthesized PEI-AuNPs with an average diameter of ~ 10 nm

Figure 54 :

 54 Figure 54: IC50 measurements on PEI coated gold nanoparticles of average size of 10 nm or 30 nm (IC50 based on gold mononuclear concentration)

  depicted great stability in saline solution and in vitro tests confirmed the biocompatibility of the smallest nanoparticles (~ 10 nm) which therefore appeared as promising cargo for further drug delivery. Comforted by previous achievement of the PEI functionalized with cytotoxic NHC-Pt moieties, and exploiting the high affinity of NHC-Pt for polyamines, coordination of wellestablished NHC-Pt complexes to gold nanoparticles has been investigated. While none of the strategies investigated to non-covalently bind NHC-Pt moieties to the nanoparticle proved successful, other paths are currently envisioned such as covalent binding of the NHC moiety to the nanoparticle through Au-S bond. Moreover, taking advantage of the positively charged synthesized nanoparticles, transfection with SiRNA will be envisioned to access gene therapy.336

  Furthermore, preliminary combination of cytotoxic NHC-Pt moieties to nanodelivery devices introduced new opportunities in the development of next generation of platinum anticancer agents. Next research efforts should be directed toward the development of safer nanoscale delivery devices in order to ultimately allow their clinical translation and use in personalized therapy. Indeed, combination of the promising NHC-Pt-PEI conjugate to synthetic peptides and proteins would allow improved potency by active targeting. Moreover, galenic formulation of the highly cytotoxic NHC-Pt-PEI conjugates could be investigated in combination with glucose to improve its bioavailability. Finally, NHC-Pt grafting onto AuNPs remains to be achieved and further decoration with biologically active moieties would give access to theranostic nanodevices for combined cancer therapy and treatment response follow up.All manipulations of air and moisture sensitive compounds were carried out using standard Schlenk techniques under an argon atmosphere and solvents were purified and degassed following standard procedures. All reagents were purchased from commercial chemical suppliers (Acros, Alfa Aesar, TCI Europe and Rapp Polymer) and used without further purification.1 H and 13 C Nuclear Magnetic Resonance (NMR) spectra were recorded on a Bruker Avance 300 or a Bruker Avance 500 spectrometer using the residual solvent peak as a reference (CDCl3: δH = 7.26 ppm; δC = 77.16 ppm) at 295 K. HMQC1 H-195 Pt spectra were recorded on a Bruker Avance 600 spectrometer using the residual solvent peak as a reference (H2PtCl6 in D2O: δPt = 0 ppm) at the Institut de Chimie NMR Facility of the University of Strasbourg. The following abbreviations are used to classify the multiplicity of the observed signals: s = singlet, d = doublet, t = triplet, m = complex multiplet and bs = broad signal. UV-visible absorption spectra were recorded on a HITACHI U-3000 spectrophotometer, fluorescence spectra on a Photon Technology International MD-5020. Positive mode electrospray ionization mass spectra (ESI-HRMS) analyses have been carried out using microTOF (Bruker Daltonics). X-Ray diffraction studies were carried out at the Institut de Chimie X-ray Facility of the University of Strasbourg.

163. 2 (

 2 C-Pt) ppm; HRMS (positive ESI): m/z calcd for C27H25SbI2N2PtNa [M + Na] 970.8691; found 970.8620; m/z calcd for C27H25SbIN2PtCH3CN [M -I + CH3CN] 862.0010; found 861.9932. ▪ Procedure E: Synthesis of Neutral NHC-Platinum-Pnictogen Complexes A solution of the corresponding trans [(NHC)PtI2(pyr)] complex (1 equiv.), [H-P(nBu)3]•BF4 (1 equiv.

8 (

 8 .1 (N-CH3), 46.4 (N-CH2), 120.6 (CHim), 121.1 (CHim), 121.9(Car), 125.6 (Car), 127.Car), 130.3(Car), 131.1(Car), 131.2(Car), 131.5(Car) ppm;[START_REF]Synthesized according to procedure C. Yellow solid, 15.4 mg[END_REF] P NMR (CDCl3, 121 MHz): δ 4.60 (1JP,Pt = 2197 Hz) ppm. HRMS (positive ESI): m/z calcd for C43H70IN2P2Pt [M -I -H] 998.3707; found 998.3703. ▪ Procedure F: Synthesis of Cationic NHC-Platinum-Pnictogen A solution of the corresponding trans [(NHC)PtI2(pyr)] (1 equiv.) and the Pnictogen ligand [2.0 equiv. in ethanol (1-5 mL)] was stirred overnight at 55 °C, under argon atmosphere. The crude mixture was then concentrated under reduced pressure and purified by silica gel chromatography (pentane/CH2Cl2, 1:1 to CH2Cl2 and CH2Cl2/MeOH, 20:1) to afford the complex as a white solid.

67.

  Synthesized according to procedure G. Red solid, 11.3 mg, yield 99%.1 H NMR (CDCl3, 300 MHz, 20 °C): δ 4.54 (s, 3H, N-CH3), 6.29 (s, 2H, N-CH2), 6.74 (d, J=2.1 Hz, 1H, CHim), 7.06 (d, J=2.1 Hz, 1H, CHim), 7.44-7.55 (m, 4H, Har), 7.93 (m, 1H, Hpyr), 8.22 (m, 2H, Hpyr), 9.67 (m, 2H, Hpyr);13 C NMR (CDCl3, 75 MHz, 20°C): δ 44.3 (s, N-CH3), 58.4 (s, N-CH2), 123.9 (CHim), 124.1(Cpyr), 124.8

( m )

 m ; HRMS (positive ESI) [M + CH3CN + Na]: C18H19Br4N5O1Pt1Na1 870.7813, found 870.7812.

70.

  Synthesized according to procedure G. Red solid, 11.5 mg, yield 99%.1 H NMR (CDCl3, 300 MHz, 20 °C): δ 4.45 (m, 6H, N-CH3), 7.46 (m, 2H, Hpyr), 7.93 (m, 1H, Hpyr), 9.65 (m, 2H, Hpyr); 13 C NMR (CDCl3, 75 MHz, 20°C): δ 29.8 (N-CH3), 43.1 (N-CH2), 110.7 (C-Pt), 120.7 (Cpyr), 124.9 (s +

  H NMR (CDCl3, MHz, 20 °C): δ 6.24 (s, 2H, N-CH2), 6.35 (s, 2H, N-CH2), 7.34-7.44 (m, 14H, Har+Hpyr), 7.74 (s, 1H, CHim), 7.96 (m, 1H, Hpyr), 9.73 (m, 2H, Hpyr); 13 C NMR (75 MHz, CDCl3, 20 °C): δ 57.5 (N-CH2), 61.4 (N-CH2), 119.5 (C-Pt), 125.1 (s + d, J=21.1 Hz, CHim), 128.3 (Car), 128.6 (Cpyr), 129.1(Car), 129.3

  H NMR at 20 °C and at a concentration of 10 -3 M of platinum. The formation of cis [(NHC)PtX2(DMSO)] species was confirmed by comparison with synthetic samples of 107 and 108. The kinetic of the reaction was monitored via integration of the 1 H NMR signals attributed to the ortho-positions in the pyridine moiety in free pyridine (δ=8.8 ppm) versus its platinum-coordinated derivative (δ=9.1 ppm) (in d6-DMSO, see example Figure A).

Figure 48 : 6 )

 486 Figure 48: Reaction progress with platinum complex 95 (representative example) at 20 °C in d6-DMSO.

Figure 49 :

 49 Figure 49: Reaction progress of platinum complex 95 with methionine (representative example) at 20°C in DMSO.

Figure 50 : 6 ▪

 506 Figure 50: Cyclic voltammetry in 0.1M TBAPF6 and acetonitrile solution at a scan rate of 100 mV.s -1 on A) NHC-Pt(IV) complexes 59 and 95, B) NHC-Pt(II) complexes 2, 4 and 6

Figure 51 :

 51 Figure 51: Cyclic voltammetry on bromine NHC-Pt(IV) complex 59 at a scan rate of 100 mV.s -1 in a 0.1 M TBAPF6 solution of a) DMSO, b) 95%DMSO/5%H2O, c) 85%DMSO/15%H2O, d) 76%DMSO/24%H2O

Figure 552 :

 552 Figure 552: Evolution complex 59 in a DMSO solution with 0.1 M TBAPF6 in the presence of one equivalent of GSH by cyclic voltammetry at 100 mV.s -1

Figure 53 :

 53 Figure 53: Evaluation of apoptosis on HCT116 p53 KO cell lines after treatment with 95, 59 or oxaliplatin at indicated concentrations (24 h of incubation). After treatment, cells were labelled Annexin V-APC and Propidium Iodide and analysed by flow cytometry. Significant flow cytometry dot plots showing apoptosis induction are represented. The percentage of early apoptotic cells (Annexin V + /PI -) and late apoptotic cells (Annexin V + /PI + ) are indicated.

109.

  Synthesized according to procedure K. UV-vis (9/1 of H2O/DMSO) λmax (nm): 239, 270.

Figure 56 :

 56 Figure 56: Evaluation of the interaction of NHC-Pt(II) complexes with BSA by UV depending on the Pt/BSA ratio for 109 (above) and 110 (below)

  H NMR (MeOD, 500 MHz, 20 °C): δ 0.66-2.11 (m, CH2,PEI), 2.37-2.91 (m, CH2,PEI), 3.06-4.12 (bs + m, NH + NHPEI overlap with MeOD), 4.79 (bs, CH2,PEI), 5.24-5.74 (m, N-CH2), 6.51 (m, CHim), 6.80 (m, CHim), 7.11-8.45 (m, 94H, CHim+Har); 13 C NMR (MeOD, 125 MHz, 20 °C): δ 10.0-

4 (

 4 Procedure M: Condensation of carboxylic acids at the PEI extremities Under argon, a solution of carboxylic acid derivative (2 equiv.) and N-hydroxysuccinimide (3 equiv.) was stirred at 20°C for 10 min. 1.55 mg of N-(3-Dimethylaminopropyl)-N′ethylcarbodiimide hydrochloride (3 equiv.) was added to the solution and stirred at 20°C for another 30min. Poly(ethyleneimine) of 25k Da (1 equiv. 83 mg, 3.32 μmol) was then added to the solution which was stirred at 50°C for three days. The resulting solution was then concentrated under reduced pressure, precipitated by addition of excess diethyl ether and further centrifuged for 10min at 10k rpm to afford the functionalized PEI as colourless oil.117. Synthesized according to procedure N. Colourless oil, quant. 1 H NMR (MeOD, 500 MHz, 20 °C): δ 1.08-1.25 (m, CH2,PEI), 2.74 (m, CH2,PEI), 3.31-3.64 (m, CH2,PEI+ CH2,PEG), 4.82 (bs, CH2,PEI+CH2,PEG+NHPEI); 13 C NMR (MeOD, 125MHz, 20 °C): δ 10.0 (CH2,PEI), 10.4 (CH2,PEI), 14.CH2,PEI), 14.5 (CH2,PEI), 15.8 (CH2,PEI), 20.0 (CH2,PEI), 23.6 (CH2,PEI), 27.0 (CH2,PEI), 28.

131.

  Synthesized according to procedure L. Light yellow oil, quant. 1 H NMR (MeOD, 500 MHz, 20 °C): δ2.27-3.03 (m, CH2,PEI), 3.49-4.23 (m, CH2,PEI+NHPEI), 5.80-5.92 (m, N-CH2), 7.40-7.61 (m, CHim + Har); 13 C NMR (MeOD, 125 MHz, 20 °C): δ 10.1-61.6 (CH2+N-CH2+N-CH3), 124.3-125.0 (CHim),129.7-130.6 (CHar), 137.1-138.3 (CHar), 161.4-164.5 (CHar+C-Pt), 171.4-177.2 (C=O).

132. 7 ( 6 ( 9 (

 769 Synthesized according to procedure L. Yellow oil, quant.1 H NMR (MeOD, 500 MHz, 20 °C): δ 1.13-1.31 (m, CH2,PEI), 2.14-3.07 (m, CH2,PEI),3.33-3.66 (m, CH2,PEI overlap MeOD), 4.02-4.24 (bs, CH2,PEI+ CH2,PEI+NHPEI+N-CH3), 5.82-5.90 (m, N-CH2), 7.29-7.77 (m, Har+Hcoumarin);13 C NMR (MeOD, 125MHz, 20 °C): δ 10.1 (CH3), 13.0 (CH3), 17.2 (CH2,PEI), 18.6 (CH2,PEI), 30.5 (CH2,PEI), 30.CH2,PEI), 41.8 (CH2,PEI),42.8 (CH2,PEI), 45.4-47.9 (CH2,PEI), 49.8 (CH2-N), 51.6-52.8 (CH2,PEI), 55.CH2,PEI), 76.1-76.4 (CH2,PEI), 112.1 (CHcoumarin), 118.9 (CHcoumarin), 125.6 (CHcoumarin), 125.CHcoumarin), 128.7 (CHcoumarin), 144.1 (CHcoumarin), 1632.9-163.4 (Ccoumarin), 171.0-171.5 (C=O).▪ Procedure N: Fluorescein thioisocyanate condensation at the NHC-Pt-PEI conJugate 113To a solution of 113(20 mg, 0.54 μmol) in DMSO (1 mL) and PBS 7.4 (2 mL) was added a solution of fluorescein isothiocyanate (0.026 mg, 0.054 μmol) in DMSO (100 μL) and stirred in the dark at 20°C, for 3 h. The solution was concentrated under reduced pressure, diluted in ethanol (0.3 mL) and subsequently dialysed toward PBS 7.4 (500 mL) at 20°C for 24h. The 133 solution was then recovered and lyophilized under reduced pressure to afford deep orange muggy solid.133.Synthesized according to procedure N. Orange oil, quant.1 H NMR (MeOD, 500 MHz, 20 °C): δ 0.81-1.19 (m, CH2,PEI), 2.87 (bs, CH2,PEI),3.22 (bs, CH2,PEI), 3.25-3.55 (m, CH2,PEI), 3.87-4.12 (m, CH2,PEI+N-CH3), 4.75 (bs, CH2,PEI+ NHPEI), 5.41-5.90 (m, N-CH2),6.41-6.42 (m, H), 7.01-8.46 (m, Har); UV-vis (EtOH) λmax (nm): 508; Fluorescence: λex=508 nm, λem=525 nm.▪ Procedure O: Condensation by intermolecular ring opening (Z)-3-(1-hydroxy-3-(naphthalen-2-yl)-3-oxoprop-1-en-1-yl)-6,6,9a-trimethyl-5,6-dihydro-2Hfuro[3,2-g]isochromene-2,9(9aH)-dione (0.12 mg, 0.27 μmol) was solubilized in 4mL of H2O/HCl (pH 2.5). A solution of 113 (10 mg, 0.27 μmol) in ethanol (1 mL) was then added and further stirred in the dark at 20°C for 24 h. The resulting solution was lyophilized under reduced pressure to afford a deep red muggy solid.

12 )

 12 Characterization of PEI-AuNPs▪ Synthesis of 10 nm PEI-AuNPsTo a solution of HAuCl4.6H20 (25 mg, 0.73 mmol, CAu = 6.4 mM) in water is added 0.02 equivalents of PEI and stirred for 30 minutes at 20°C. Then, a solution of TBAB (0.01 equivalents)

Figure 54 :Figure 55 :Figure 56 :Figure 58 :Figure 57 :Figure 58 :Figure 59 :

 54555658575859 Figure 54: UV-vis spectra of ~10 nm PEI-AuNPs

  230,231 It has been widely used as a representative model for preliminary investigation of NHC-Pt(IV) bioreduction in the literature (i.e. 1:2-25 Pt/reducing agent ratio, r.t. to 37 °C).232,233,234

  2 2 E. Chardon, G. Dahm, G. Guichard, S. Bellemin-Laponnaz Chem. Asian J. 2013, 8, 1232-1242 1. Synthesized according to procedure B. Yellow solid, 23.3 mg, yield 24%.1 H NMR (CDCl3, 300

  according to procedure B. Yellow solid, 25.2 mg, yield 26%.1 H NMR (CDCl3, 300

	6. Synthesized according to procedure B. Yellow solid, 65 mg, yield 51%. 1 H NMR (CDCl3, 300
	MHz, 20 °C): δ 0.95 (t, J=6.7 Hz, 3H, CH3), 1.41 (m, 4H, CH2), 2.03 (q, J=7.6 Hz, 2H, CH2), 3.94 (s,
	3H, N-CH3), 4.41 (t, J=7.6 Hz, 2H, N-CH2), 6.83 (s, 2H, CHim), 7.31 (t, J=6.7 Hz, 2H, Hpyr), 7.71 (tt,
	J1=7.8 Hz, J2=1.6 Hz, 1H, Hpyr), 9.02 (m, 2H, Hpyr); 13 C NMR (CDCl3, 75 MHz, 20 °C): δ 14.1 (CH3),
	4. Synthesized according to procedure B. Yellow solid, 47.3 mg, yield 43%. 1 H NMR (CDCl3, 300 22.3 (CH2), 28.9 (CH2), 29.3 (CH2), 38.4 (N-CH3), 50.9 (N-CH2), 120.4 (CHim), 121.9 (CHim), 125.0
	MHz, 20 °C): δ 0.91 (t, J=6.7 Hz, 3H, CH3), 1.38 (m, 4H, CH2), 2.01 (m, 2H, CH2), 4.02 (s, 3H, N-(Cpyr), 135.1 (C-Pt), 137.5 (Cpyr), 153.7 (Cpyr). MS (positive ESI) [M-I]: calculated for C14H21I1N3Pt1:
	CH3), 4.46 (m, 2H, N-CH2), 6.82 (s, 2H, CHim), 7.31 (t, J=7.0 Hz, 2H, CHpyr), 7.73 (t, J=7.6 Hz, 1H, 553.04, found 553.04, [M-I + CH3CN]: calculated for C14H21I1N3Pt1CH3CN: 594.07, found 594.07.
	CHpyr), 8.98 (m, 2H, CHpyr); 13 C NMR (CDCl3, 75 MHz, 20 °C): 14.0 (CH3), 22.3 (CH2), 28.7 (CH2),
	29.9 (CH2), 37.8 (N-CH3), 50.6 (N-CH2), 120.4 (CHim), 121.8 (CHim), 124.9 (CHpyr), 136.9 (C-Pt),
	137.7 (CHpyr), 152.5 (CHpyr).
	MHz, 20 °C): δ 0.94 (t, J=6.5 Hz, 3H, CH3), 1.42 (m, 4H, CH2), 2.03 (m, 2H, CH2), 4.09 (s, 3H, N-
	CH3), 4.51 (m, 2H, N-CH2), 6.85 (s, 2H, CHim), 7.36 (M, 2H, CHpyr), 7.76 (t, J=7.6 Hz, 1H, CHpyr),
	9.03 (m, 2H, CHpyr). 7. Synthesized according to procedure B. Yellow solid, 109.1 mg, yield 93%. 1 H NMR (CDCl3, 300
	MHz, 20 °C): δ 3.93 (d, J=0.7 Hz, 6H, N-CH3), 6.82 (d, J=0.7 Hz, 2H, CHim), 7.31 (t, J=6.8 Hz, 2H,
	Hpyr), 7.71 (td, J1=7.6 Hz, J2=0.7 Hz, 1H, Hpyr), 9.02 (m, 2H, 2Hpyr); 13 C NMR (CDCl3, 75 MHz, 20 °C):
	δ 38.2 (N-CH3), 121.9 (CHim), 125.0 (Cpyr), 135.9 (C-Pt), 137.5 (Cpyr), 153.7 (Cpyr).
	5. Synthesized according to procedure B. Yellow solid, 94.7 mg, yield 72%. 1 H NMR (CDCl3, 300
	MHz, 20 °C): δ 3.97 (s, 3H, N-CH3), 5.72 (s, 2H, N-CH2), 6.60 (s, 1H, CHim), 6.82 (s, 1H, CHim), 7.27-
	7.44 (m, 5H, Har), 7.52 (m, 2H, Hpyr), 7.74 (m, 1H, Hpyr), 9.09 (m, 2H, Hpyr); 13 C NMR (CDCl3, 75
	3. Synthesized according to procedure B. Yellow solid, 59.2 mg, yield 52%. 1H NMR (CDCl3, 300 MHz, 20 °C): δ 38.3 (N-CH3), 54.4 (N-CH2), 119.8 (CHim), 122.2 (CHim), 124.8 (Cpyr), 128.3 (Car),
	MHz, 20 °C): δ 4.11 (s, 3H, N-CH3), 5.83 (s, 2H, N-CH2), 6.64 (d, J= 2.1Hz, 1H, CHim), 6.83 (d, J=2.1 128.8 (Car), 129.1 (s, CHar), 135.4 (Cpyr), 136.3 (C-Pt), 137.5 (s, Cpyr), 153.7 (Cpyr); MS (positive ESI)
	Hz, 1H, CHim), 7.27-7.53 (m, 7H, 5Har and 2Hpyr), 7.76 (tt, J1=7.6 Hz, J2=1.6 Hz, 1H, Hpyr), 9.04 (dt, [M-I]: calculated for C16H17IN3Pt: 573.011, found 572.969. Microanalysis: Calculated for 8. Synthesized according to procedure B. Yellow solid, 56.8 mg, yield 35%. 1 H NMR (CDCl3, 300
	J1=5.0 Hz, J2=1.6 Hz, 2H, 2Hpyr); 13 C NMR (CDCl3, 75 MHz, 20 °C): δ 37.9 (N-CH3), 54.2 (N-CH2), C16H17I2N3Pt: C, 27.44; H, 2.45; N, 6.00. Found: C, 26.97; H, 2.47; N, 5.82. MHz, 20 °C): δ 0.87 (t, J=6.7 Hz, 3H, CH3), 1.25 (m, 30H, CH2), 2.03 (m, 2H, CH2), 3.95 (s, 3H, N-
	120.0 (CHim), 122.4 (CHim), 124.9 (Cpyr), 128.2 (CHar), 128.8 (CHar), 128.8 (CHar), 135.7 (Car), 137.7 CH3), 4.42 t, J=7.7 Hz, 2H, N-CH2), 6.83 (s, 2H, CHim), 7.31 (m, 2H, Hpyr), 7.71 (tt, J1=7.7 Hz, J2=1.6
	(Cpyr), 138.2 (C-Pt), 152.6 (Cpyr); 13 C NMR (Acetone, 75 MHz, 20 °C): δ 37.1 (N-CH3), 53.5 (N-CH2), Hz, 1H, Hpyr), 9.04 (m, 2H, Hpyr); 13 C NMR (CDCl3, 75 MHz, 20 °C): δ 14.1 (CH3),
	120.3 (CHim), 123.0 (CHim), 125.1 (Cpyr), 127.9 (CHar), 128.5 (CHar), 128.8 (CHar), 136.8 (Car), 138.3
	(Cpyr), 152.5 (Cpyr); HMQC 1 H-195 Pt NMR (CDCl3, 64.2 MHz, 20 °C): δ -3814 (m).

  Synthesized according to procedure C. Yellow solid, 15.4 mg, quant.1 H NMR (CDCl3, 300

	39. Synthesized according to procedure C. Yellow solid, 10 mg, yield 58%. 1 H NMR (CDCl3, 300
	MHz, 20 °C): δ δ 1.05-1.35 (m, 5H, CH2), 1.55-1.87 (m, 3H, CH2), 2.25 (d, J=11.7 Hz, 2H, CH2), 2.95 MHz, 20 °C): δ 0.87 (t, J=6.6 Hz, 3H, CH3), 1.25 (m, 30H, CH2), 1.95 (m, 2H, CH2), 2.88 (m, 2H,
	(m, 2H, NH2), 3.27 (m, 1H, CH), 3.90 (s, 3H, N-CH3), 5.70 (s, 2H, N-CH2), 6.63 (s, 1H, CHim), 6.85 (s, CH2), 3.30 (bs, 1H, NH), 3.50-3.63 (m, 4H, CH2), 3.82-4.03 (s+m, 5H, N-CH3 overlap CH2), 4.27 (m,
	1H, CHim), 7.59 (d, J=8.1 Hz, 2H, Har), 7.87 (d, J=8.1Hz, 2H, Har), 10.01 (s, 1H, CHO); 13 C NMR 2H, N-CH2), 6.78 (s, 2H, CHim); 13 C NMR (CDCl3, 75 MHz, 20 °C): δ 13.1 (CH3), 21.7 (CH2), 23.8
	(CDCl3, 75 MHz, 20 °C): δ 24.8 (CH2), 25.3 (CH2), 35.9 (CH2), 38.3 (N-CH3), 53.9 (CH), 54.9 (N-CH2), 120.0 (CHim), 122.6 (CHim), 129.3 (Car), 130.1 (Car), 136.2 (Car), 141.1 (C-Pt), 142.2 (Car),191.7 (CHO); MS (positive ESI) [M-I]: calculated for C18H25I1N3O1Pt1 621.069 found 621.072, [M-I+CH3CN]: calculated for C18H25I1N3O1Pt1CH3CN 662.095, found 662.096. 37. Synthesized according to procedure C. Yellow solid, 17.6 mg, yield 58%. 1 H NMR (CDCl3, 300 MHz, 20 °C): δ 2.92 (d, J=11.4 Hz, 2H, CH2), 3.15-3.45 (m, 1H, NH), 3.46-3.71 (m, 4H, CH), 3.82 (d, J=12.3 Hz, 2H, CH2), 3.86 (s, 3H, N-CH3), 5.56 (s, 2H, N-CH2), 6.56 (s, 1H, CHim), 6.77 (s, 1H, CHim), (CH2), 24.3 (CH2), 25.7 (CH2), 28.1 (CH2), 28.2 (CH2), 28.3 (CH2), 28.4 (CH2), 28.5 (CH2), 28.6 (CH2), 28.7 (CH2), 29.9 (CH2), 30.9 (CH2), 34.8 (N-CH3), 37.0 (CH2), 49.7 (CH2), 52.4 (HN-CH), 53.8 (N-CH2), 119.2 (CHim), 120.6 (CHim), C-Pt could not be seen. 45. Synthesized according to procedure C. Yellow solid, 8.7 mg, yield 52%. 1 H NMR (CDCl3, 300 50. Synthesized according to procedure C. Yellow oil, 7.8 mg, yield 52%. 1 H NMR (CDCl3, 300 MHz, 20 °C): δ 0.88 (t, J=6.7 Hz, 6H, CH3), 1.26-1.37 (m, 48H, CH2), 1.60-1.67 (m, 2H, CH2), 1,.96 MHz, 20°C): δ 3.99 (s, 6H, N-CH3), 5.72 (s, 4H, N-CH2), 6.74 (d, J=2.1 Hz, 2H, CHim), 6.81 (d, J=2.1 (m, 2H, CH2), 2.92-2.99 (m+bs, 4H, H2N-CH2), 3.84 (s, 3H, N-CH3), 4.30 (m, 2H, N-CH2), 6.79 (s, Hz, 2H, CHim), 7.32 (m, 4H, Hpyr), 7.39 (m, 1H, Har), 7.50-7.58 (m, 3H, Har), 7.71 (m, 2H, Hpyr), 9.04 2H, CHim). (m, 4H, Hpyr).
	7.28-7.48 (m, 5H, Har); 13 C NMR (CDCl3, 75 MHz, 20 °C): δ 38.2 (N-CH3), 50.6 (CH2), 54.5 (CH2),
	68.7 (CH2), 120.0 (CH), 122.3 (CH), 128.3 (CHaromatic), 128.8 (CHaromatic), 129.1 (CHaromatic), 135.3
	(Caromatic), 136.3 (C-Pt). HRMS (positive ESI) [M+Na]: calcd for C15H21I2N3OPt.Na 730.932, found 48. Synthesized according to procedure C. Yellow oil, 11.3 mg, yield 32%. 1 H NMR (CDCl3, 300
	MHz, 20 °C): δ 0.87 (t, J=6.6 Hz, 6H, CH3), 1.23-1.43 (m, 28H, CH2), 1.80 (m, 2H, CH2), 2.15 (m, 730.929. 40. Synthesized according to procedure C. Yellow solid, 19 mg, yield 65%. 1 H NMR (CDCl3, 300 2H, CH2), 2.81 (m, 2H, CH2), 3.28 (m, 3H, NH+CH2), 3.88 (s, 3H, N-CH3), 5.85 (s, 2H, N-CH2), 6.55
	MHz, 20 °C): δ 0.94 (t, 3H, CH3), 1.25-1.40 (m, 2H, CH2), 1.60 (m, 2H, CH2), 2.99 (bs, 4H, (d, J=2.1 Hz, 1H, CHim), 6.77 (d, J=2.1 Hz, 1H, CHim), 7.33-7.49 (m, 5H, CHar); 13 C NMR (CDCl3, 75
	35. Synthesized according to procedure C. Yellow solid, 15.3 mg, 84%. 1 H NMR (CDCl3, 300 MHz, CH2+NH2), 3.89 (s, 3H, N-CH3), 5.59 (s, 2H, N-CH2), 6.56 (d, J=2.1 Hz, 1H, CHim), 6.77 (d, J=2.1 Hz, MHz, 20 °C): δ 14.1 (CH3), 22.6 (CH2), 26.9 (CH2), 28.9 (CH2), 29.3 (CH2), 29.3 (CH2), 29.4 (CH2),
	20 °C): δ 1.11-1.80 (m, 8H, CH2), 2.27 (m, 2H, CH2), 2.96 (m, 2H, NH2), 3.24 (m, 1H, CH), 3.86 (s, 1H, CHim), 7.34-7.46 (m, 5H, Har); 13 C NMR (CDCl3, 75 MHz, 20 °C): δ 13.8 (CH3), 19.8 (CH2), 31.1 29.5 (CH2), 31.9 (CH2), 37.9 (N-CH3), 54.1 (N-CH2), 55.1 (N-CH2), 119.7 (CHim), 122.1 (CHim), 128.2
	6H, N-CH3); 13 C NMR (CDCl3, 75 Mz, 20 °C): δ 25.0 (CH2), 25.4 (CH2), 36.0 (CH2), 36.4 (N-CH2), (CH2), 34.4 (CH2), 38.3 (CH3), 45.3 (CH2), 54.6 (N-CH2), 120.0 (CHim), 122.4 (CHim), 128.4 (Car), (CDCl3, 75 MHz, 20 °C): δ 38.3 (CH2), 45.2 (CH2), 54.5 (N-CH3), 59.1 (CH2), 70.3 (N-CH2), 70.7 (CHar), 128.8 (CHar), 129.1 (CHar), 135.4 (Car), 138.7 (C-Pt).
	55.2 (CH2), 116.1 (Cim), 141.3 (C-Pt). 128.9 (Car), 129.2 (Car), 135.6 (Car), 139.7 (C-Pt). (CH2), 72.1 (CH3), 119.9 (CHim), 122.3 (CHim), 128.4 (CHar), 128.9 (CHar), 129.1 (CHar), 135.6 (Car),
	38. Synthesized according to procedure C. Yellow solid, 15.1 mg, yield 58%. 1 H NMR (CDCl3, 300 139.7 (C-Pt).
	MHz, 20 °C): δ 0.92 (t, J=6.7 Hz, 3H, CH3), 1.38 (m, 4H, CH2), 1.95 (m, 2H, CH2), 2.87 (d, J=12.9 Hz,
	2H, CH2), 3.27 (bs, 1H, NH), 3.49-3.66 (m, 4H, CH2), 3.80 (s+m, 5H, N-CH3+CH2), 4.27 (m, 2H, N-
	CH2), 6.79 (s, 2H, CHim); 13 C NMR (CDCl3, 75 MHz, 20 °C): δ 14.1 (CH3), 22.3 (CH2), 28.9 (CH2), 29.3
	(CH2), 38.3 (N-CH3), 50.6 (CH2), 50.9 (H2N-CH), 68.9 (N-CH 2), 120.4 (CHim), 121.9 (CHim), 135.0 (C-41. Synthesized according to procedure C. Yellow solid, 18,1 mg, yield 61%. 1 H NMR (CDCl3, 300 49. Synthesized according to procedure C. Yellow oil, 6.8 mg, yield 27%. 1 H NMR (CDCl3, 300
	36. Synthesized according to procedure C. Yellow solid, 25.4 mg, quant. 1 H NMR (CDCl3, 300 Pt). MHz, 20 °C): δ 0,90-0,97 (q, 6H, CH3), 1,36-1,43 (m, 6H, CH2), 1,56-1,62 (m, 2H, CH2), 1,96 (m, 47. Synthesized according to procedure C. Yellow oil, 4,9 mg, yield 36%. 1 H NMR (CDCl3, 300 MHz, 20 °C): δ 2.68 (m, 4H, CH2), 3.35 (bs, 2H, NH2), 3.68 (s, 3H, N-CH3), 3.88-3.96 (s+m, 5H,
	MHz, 20 °C): δ 2.88 (d, J=11 Hz, 2H, CH), 3.25 (bs, 1H, NH), 3.52-3.57 (m, 4H, CH), 3.81 (s, 6H, N-2H, CH2), 2,89-3,04 (m+bs, 4H, H2N-CH2), 3,84 (s, 3H, N-CH3), 4,30 (m, 2H, N-CH2), 6,79 (s, 2H, MHz, 20 °C): δ 0.89 (t, J=6,8Hz, 3H, CH3), 1.28 (m, 28H, CH2), 1.95 (m, 2H, CH2), 3.20 (bs, 2H, CH3+CH2), 5.58 (s, 2H, N-CH2), 6.57 (d, J=2.1 Hz, 1H, CHim), 6.78 (d, J=2.1 Hz, 1H, CHim), 7.34-7.42
	CH3), 6.78 (s, 2H, CHim); 13 C NMR (CDCl3, 75 MHz, 20 °C): δ 38.1 (N-CH3), 50.6 (CH2), 68.8 (CH2), CHim); 13 C NMR (CDCl3, 75 MHz, 20 °C): δ 14.9 (CH3), 14.1 (CH3), 19.8 (CH2), 22.4 (CH2), 28.9 NH2), 3.35 (s, 3H, O-CH3), 3.62 (m, 70H, CH2), 3.84 (s, 3H, N-CH3), 4.31 (m, 2H, N-CH2), 6.86 (s, (m, 5H, CHar); 13 C NMR (CDCl3, 75 MHz, 20°C): δ 27.6, 29.8, 34.4, 38.4, 52.2, 53.9, 54.6, 120.1
	121.8 (CHim), 135.8 (C-Pt). (CH2), 29.5 (CH2), 34.3 (CH2), 38.3 (CH3), 45.3(CH2), 50.9 (CH2), 120.4 (s+d, J=30.6 Hz, CHim), 121.8 2H, CHim); 13 C NMR (CDCl3, 75 MHz, 20 °C): δ 14.3 (CH3), 23.0 (CH2), 27.1 (CH2), 29.6 (CH2), 29.7 (CHim), 122.4 (CHim), 128.5 (CHar), 128.9 (CHar), 129.1 (CHar), 135.4 (Car), 138.1 (C-Pt), 127.7 (CO).
	(s+d, J=30.6 Hz, CHim), 138.4 (C-Pt). (CH2), 29.8 (CH2), 29.9 (CH2), 30.1 (CH2), 30.9 (CH2), 32.3 (CH2), 38.3 (CH2), 45.5 (CH2), 51.0 (N-
	CH3), 70.6 (N-CH2), 72.3 (O-CH3), 120.6 (CHim), 120.0 (CHim), 138.9 (C-Pt).

34.

46. Synthesized according to procedure C. Yellow oil, 28 mg, yield 47%.

1

H NMR (CDCl3, 300 MHz, 20 °C): δ 3.37 (s, 3H, OCH3), 3.63-3.66 (m, 68H, CH2 + NH2), 3.87 (s, 3H, N-CH3), 5.58 (s, 2H, N-CH2),

6.55 (d, J=2.1 Hz, 1H, CHim), 6.77 (d, J=2.1 Hz, 1H, CHim), 7.33-7.42 (m, 5H, CHar)

;

13

C NMR

  , 7.80 (s, 1 H, CHim) ppm;31 P NMR (CDCl3, 121 MHz, 20°C): δ 4.63 (1JP,Pt = 2196 Hz) ppm;13 C NMR (CDCl3, 75 MHz, 20°C): δ 13.7, 14.2, 19.8, 22.8, 23.6, 23.8, 24.2 (t, J=7.1 Hz, P-CH2), 26.5 (t, J=10 Hz, P-CH2), 29.5 (CH2), 29.8 (CH2), 30.1 Synthesized according to procedure E. Yellow solid, 8.3 mg, yield 24%.

	(CH2), 32.0 (CH2), 37.2 (CH3), 38.2 (N-CH3), 53.8 (N-CH2), 122.1 (CHim), 125.7 (CHim), 126.9 (Car),
	129.0 (Car), 129.6 (Car), 133.5 (Car) ppm; the signal for the (CPt) carbon was not observed; HRMS
	(positive ESI): m/z calcd for C35H66IN2P2Pt [M -I-(C6H14)] 898.3494; found 898.3650.
	55.

1 H NMR (CDCl3, 300

MHz, 20°C): δ 1.

20-1.54 (m, 27 H, nBu)

, 4.07 (s, 3 H, N-CH3), 5.91 (s, 2 H, N-CH2), 6.05 (s, 1 H, CHim), 7.52-7.61

(m, 4 H, HAr), 7.66 (s, 1 H, CHim), 7.85 (d, 2 H, HAr), 8.16 (d, 2 H, HAr), 8.71 (s, 1 H, HAr)

ppm;

13

C NMR (CDCl3, 75 MHz, 20°C): δ 13.

  Synthesized according to procedure G. Red solid, 12.3 mg, yield 99%.1 H NMR (CDCl3, 300 MHz, 20 °C): δ 4.50 (s, 3H, N-CH3), 6.23 (s, 2H, N-CH2), 6.74 (q, J1=4.8 Hz, J2=2.5 Hz, 1H, CHim), 7.03 (q, J1=4.8 Hz, J2=2.5 Hz, 1H, CHim), 7.45 (dd, 2H, Har), 7.52 (d, 2H, Har), 7.87-7.94 (m, 3H, C NMR (CDCl3, 75 MHz, 20°C): δ 31.0, 44.6, 59.1, 110.6 (s+d, J=1034 Hz, C-Pt), 124.8 (CHim), 125.2 (Cpyr), 126.6 (CHim), 129.3 (CHar), 130.2 (CHar), 136.5 (CHar), 140.2(Cpyr), 143.7 (Cpyr), 191.2 (CHO).

	64. Synthesized according to procedure G. Red solid, 10.7 mg, yield 98%. 1 H NMR (CD2Cl2, 500 MHz, 20 °C): δ 4.45 (s, 3H, N-CH3), 6.09 (s, 2H, N-CH2), 6.78 (d, J = 2.1 Hz, 1H, CHim), 7.01 (d, J=2.1 Hz, 1H, CHim), 7.32-7.37 (m, 7H, Har), 7.46 (m, 2H, Hpyr), 7.94 (m, 1H, Hpyr), 9.64 (m, 2H, Hpyr); 13 C NMR (CD2Cl2, 125 MHz, 20 °C): δ 44.1 (N-CH3), 59.1 (N-CH2), 109.3 (C-Pt), 124.4 (s + 66. Hpyr), 9.63-9.72 (m, 2H, Hpyr), 10.02 (s, 1H, CHO); 13 C NMR (CDCl3, 75 MHz, 20°C): δ 44.3 (N-CH3),
	62. Synthesized according to procedure G. Red solid, 11.2 mg, yield 96%. 1 H NMR (CDCl3, 300 d, J=10.8 Hz, CHim), 124.8 (CHar), 125.7 (s + d, J=10.8 Hz, CHim), 128.7 (CHar), 128.8 (CHar), 136.7 58.9 (N-CH2), 110.8 (C-Pt), 124.1 (t, J=10.8Hz, CHim), 124.8 (t, J=18.9Hz, Cpyr), 125.8 (t, J=10.8 Hz,
	MHz, 20 °C): δ 1.85 (m, 6H, CH2), 2.57 (m, 2H, CH2), 4.41 (s, 3H, N-CH3), 6.17 (m, 1H, N-CH), 7.05 (Cpyr), 139.8 (Cpyr), 154.3 (Cpyr); HMQC 1 H-195 Pt NMR (CDCl3, 64.2 MHz, 20 °C): δ -2048 (m); MS CHim), 129.1 (CHar), 130.1 (CHar), 136.2 (Car), 139.5 (Cpyr), 143.0 (Car), 154.4 (Cpyr), 191.6 (CHO);
	(d, J=2.1 Hz, 1H, CHim), 7.07 (d, J=2.1 Hz, 1H, CHim), 7.47 (m, 2H, Hpyr), 7.92 (m, 1H, Hpyr), 9.64 (m, (positive ESI) [M -3Br]: C16H16Br1N3Pt1: 523.01, found 524.01; elemental anal. calc. for
	2H, Hpyr); no 13 C NMR spectrum could be recorded due to very low solubility; HMQC 1 H-195 Pt C16H17Br4N3Pt1: C 25.09, H 2.24, N 5.49, found: C 24.74, H 2.23, N 5.40.
	NMR (CDCl3, 64.2 MHz, 20 °C): δ -2032 ppm (m); MS (positive ESI) [M -2Br]:
	C14H18Br2N3Pt1 580.95, found 582.95; elemental anal. calc. for C14H19Br4N3Pt + Br2: C 18.60, H
	2.12, N 4.65, found: C 18.42, H 2.13, N 4.51.	H NMR (CDCl3, 300
	MHz, 20 °C): δ 4.46 (m, 6H, N-CH3), 7.02 (d, J=2.1 Hz, 2H, CHim), 7.45 (m, 2H, Hpyr), 7.91 (m, 1H,
	63. Synthesized according to procedure G. Red solid, 16.7 mg, yield 99%. 1 H NMR (CDCl3, 300 MHz, 20 °C): δ 3.97 (N-CH3), 5.23 (s, 2H, N-CH2), 6.87 (d, J=2.1 Hz, 1H, CHim), 7.01 (d, J=2.1 Hz, 1H, CHim), 7.32 (m, 2H, Hpyr), 7.73 (m, 1H, Hpyr), 9.03 (m, 2H, Hpyr); 13 C NMR (CDCl3, 75 MHz, 20 °C): δ 28.0 (CtBu), 44.1 (N-CH3), 56.7(N-CH2), 124.7(s + d, J=20.2 Hz, CHim), 126.4 (Cpyr), 139.4 65. Synthesized according to procedure G. Red solid, 12.2 mg, yield 99%. 1 H NMR (CDCl3, 300 MHz, 20 °C): δ 6.23 (s, 2H, N-CH2), 6.84 (d, J=2.1 Hz, 1H, Him), 6.91 d, J=2.1 Hz, 1H, Him), 7.35-7.54 (m, 10H, Har), 7.75 (m, 2H, Hpyr), 7.84 (m, 1H, Hpyr), 9.34 (m, 2H, Hpyr); 1 H NMR (CD2Cl2, 300 MHz, 20 °C): δ (s, 2H, N-CH2), (d, J=2.0 Hz, 1H, CHim), (d, J=2.0 Hz, 1H, CHim), (m, 11H, CHar+CHpyr, overlap CDCl3), (m, 2H, Hpyr), (m, 2H, Hpyr); 13 C NMR (CD2Cl2, 75 MHz, 20 °C): δ 55.0 (N-CH2), 114.2 (CHim), 117.2 (CHim), 123.8 (Cpyr), 126.1 (Cpyr), 127.1 (CHar), 128.9 (CHar), 129.3 (CHar), 130.3 (CHar), 135.8 (Car), 140.3 (N-Car), 141.5 (CHar), 153.7 (Cpyr), (C-Pt) not seen; MS (positive ESI) [M -Hpyr), 9.70 (m, 2H, Hpyr); 59. Synthesized according to procedure G. Red solid, 11.6 mg, yield 99%. 1 H NMR (CDCl3, 300 CH3), 4.78 (m, 2H, N-CH2), 7.03 (d, J=2.1 Hz, 1H, CHim), 7.12 (d, J=2.1 Hz, 1H, CHim), 7.44 (m, 2H, 2070(m). MHz, 20 °C): δ 0.93 (t, J=7.0 Hz, 3H, CH3), 1.43 (m, 4H, CH2), 1.92 (m, 2H, CH2), 4.44 (s, 3H, N-(Cpyr), 154.4 (Cpyr), (C-Pt) and (C=O) not seen; HMQC 1 H-195 Pt NMR (CDCl3, 64.2 MHz, 20 °C): δ -2Br]: C21H19Br2N3Pt1 667.963, found 667.952.
	Hpyr), 7.89 (m, 1H, Hpyr), 9.71 (m, 2H, Hpyr); 13 C NMR (CDCl3, 75 MHz, 20 °C): δ 14.2 (CH3), 22.6
	(CH2), 28.8 (CH2), 44.2 (N-CH3), 55.4 (N-CH2), 109.2 (C-Pt), 123.5 (s + d, J=11.1 Hz, CHim), 124.7
	(s + d, J=9.9 Hz, Cpyr), 125.8 (s + d, J=11.1 Hz, CHim), 139.5 (Cpyr), 154.6 (Cpyr); HMQC 1 H-195 Pt
	NMR (CDCl3, 64.2 MHz, 20 °C): δ -2040 ppm (m); HRMS (positive ESI) [M + Na]:

13

C NMR (CDCl3, 75 MHz, 20 °C): δ 44.3 (N-CH3), 53.6 (N-CH2), 120.7 (C-Pt), 124.9 (s + d, J=19.3 Hz, CHim), 125.7 (s + d, J=22.1 Hz, CHim), 139.6 (Cpyr), 154.6 (s + d, J=4.6 Hz, Cpyr); HRMS (positive ESI) [2M+Na]: C20H26Br8N6Pt2Na1: 1394.4822, found 1394.5160.

13

  : δ 0.80-2.11 (m, CH2,PEI), 2.36-2.93 (m, CH2,PEI), 3.06-4.11 (bs + m, CH2,PEI+NHPEI overlap with MeOD), 4.79 (bs, CH2,PEI), 5.69 (m, N-CH2),6.51

  H NMR (MeOD, 500 MHz, 20 °C): δ 0.68-2.11 (m, CH2,PEI), 2.34-2.85 (m, CH2,PEI), 3.15-4.31 (bs + m, NH + NHPEI overlap with MeOD), 4.80 (bs, CH2,PEI), 5.24-5.67 (m, N-CH2), 6.51

  8 (CH2,PEI),29.8- 31.1 (CH2,PEI), 32.8 (CH2,PEI), 33.9 (CH2,PEI), 34.6 (CH2,PEI), 35.1 (CH2,PEI), 35.6 (CH2,PEI), 35.7 (CH2,PEI), 39.1 (CH2,PEI), 40.0 (CH2,PEI), 40.1 (CH2,PEI), 41.6 (CH2,PEI), 45.4 (CH2,PEI), 45.8 (CH2,PEI), 46.6-49.9 (CH2,PEI + MeOD), 52.4 (CH2,PEG), 54.9 (CH2,PEG), 57.5 (CH2,PEG), 57.9 (CH2,PEG), 59.0 (CH2,PEG), 60.7 (CH2,PEG), 61.4 (CH2,PEG), 64.3 (CH2,PEG), 70.4 (CH2,PEG), 71.1 (CH2,PEG), 71.3 (CH2,PEG), 73.6 (CH2,PEG), 79.1 (CH2,PEG), C=O could not be seen. Chapter 5 Experimental part 239 125 MHz, 20 °C): δ 9.0 (CH2,PEI), 13.3 (CH2,PEI), 14.6 (CH2,PEI), 22.4 (CH2,PEI), 25.6 (CH2,PEI), 25.7(CH2,PEI), 25.9 (CH2,PEI), 26.8 (CH2,PEI), 27.6 (CH2,PEI), 28.9-29.9 (CH2,PEI), 31.7 (CH2,PEI), 34.5 (CH2,PEI), 36.2 (CH2,PEI), 37.9 (CH2,PEI), 38.4 (CH2,PEI),42.9-48.4 (CH2,PEI+MeOD), 50.1 (CH2,PEG), 55.1 (CH2,PEG), 56.7 (CH2,PEG), 60.9 (CH2,PEG), 68.5 (CH2,PEG), 69.7-70.2 (CH2,PEG), 72.4 (CH2,PEG), 159.6 (C=O).119. Synthesized according to procedure N. Colourless oil, quant.1 H NMR (MeOD, 500 MHz, 20 °C): δ 0.87 (t, J=6.7 Hz, CH3alc), 1.09 (m, CH2PEI + CH2alc), 1.23 (q, J1=14.1 Hz, J2=6.7 Hz, overlap m, CH2PEI + CH2alc), 1.56-1.88 (m, CH2,PEI), 2.24-2.57 (m, CH2,PEI), 2.75-2.87 (m, CH2,PEI), 3.28-3.72 (m, CH2,PEI), 4.11 (bs, CH2,PEI+NHPEI).120. Synthesized according to procedure N. Colourless oil, quant. 1 H NMR (MeOD, 500 MHz, 20 °C): δ 1.11-1.28 (m, CH2,PEI+CH2,adamantyl), 1.72-1.75 (bs, CH2,PEI+CH2,adamantyl), 2.25 (m, CH2,PEI), 2.38-2.54 (m, CH2,PEI), 2.73-2.81 (m, CH2,PEI), 3.32-3.75 (m, CH2,PEI), 4.11 (m, CH2,PEI+NHPEI).121. Synthesized according to procedure N. Colourless oil, quant. 1 H NMR (MeOD, 500 MHz, 20 °C): δ 1.10-1.31 (m, CH2,PEI+CH2,alc), 1.77-2.74 (m, CH2,PEI+CH2,alc), 3.21-3.71 (m, CH2,PEI), 4.13-4.21 (bs, CH2,PEI+NHPEI).122. Synthesized according to procedure N. Light yellow oil, quant. 1 H NMR (MeOD, 500 MHz, 20 °C): δ 1.10-1.31 (m, CH2,PEI), 1.61-1.87 (m, CH2,PEI), 2.23-2.25 (m, CH2,PEI), 2.34-2.84 (m, CH2,PEI), 3.19-3.70 (m, CH2,PEI + NH2,PEI), 3.96-4.10 (bs, CH2,PEI+NHPEI), 7.49 (m, CHanthracene), 8.05 (m, CHanthracene), 8.21-8.23 (m, CHanthracene), 8.41 (m, CHanthracene); 13 C NMR (MeOD, 125 MHz, 20 °C): δ 9.9 (CH2,PEI), 10.1 (CH2,PEI), 14.4 (CH2,PEI), 14.6 (CH2,PEI), 15.8 (CH2,PEI), 18.1 (CH2,PEI), 26.7-27.0 (CH2,PEI), 31.2 (CH2,PEI), 36.8 (CH2,PEI), 37.3 (CH2,PEI), 40.6 (CH2,PEI), 44.1 (CH2,PEI), 44.8 (CH2,PEI), 45.6 (CH2,PEI), 45.8 (CH2,PEI), 45.9 (CH2,PEI), 46.8 (CH2,PEI), 47.2 (CH2,PEI), 47.8 (CH2,PEI), 48.8-49.1 (CH2,PEI), 56.1-56.8 (CH2,PEI), 58.1 (CH2,PEI), 160.7 (CHanthracene), 163.2.6-163.1 (Canthracene), 163.3 Synthesized according to procedure N. Light yellow oil, quant. 1 H NMR (MeOD, 500 MHz, 20 °C): δ 1.1-1.23 (m, CH2,PEI), 1.74 (m, CH2,PEI), 2.23 (s, CH2,PEI), 2.37-2.43 (m, CH2,PEI), 2.50-2.54 (m, CH2,PEI),3.20-3.38 (m, CH2,PEI+MeOD), 4.10-4.22 (bs, CH2,PEI+NHPEI), 6.93 (m, CHfluorene), 7.35-7.52 (m, CHfluorene), 7.85 (m, CHfluorene);13 C NMR (MeOD, 125MHz, 20 °C): δ 14.6 (CH2,PEI),18.5

	(CH2,PEI), 26.8 (CH2,PEI), 26.9 (CH2,PEI), 35.7 (CH2,PEI), 37.3 (CH2,PEI), 37.4-37.6 (CH2,PEI), 40.9 (CH2,PEI),
	44.1 (CH2,PEI), 44.7-44.9 (CH2,PEI), 47.8-49.8 (CH2,PEI + MeOD), 56.2 (CH2,PEI), 58.1 (CH2,PEI), 61.2
	(CH2,PEI), 61.3 (CH2,PEI), 158.2 (CHfluorene), 157.0 (CHfluorene), 159.9-160.7 (CHfluorene), 162.9-163.3

118. Synthesized according to procedure N. Colourless oil, quant.

1

H NMR (MeOD, 500 MHz, 20 °C): δ 2.73 (m, CH2,PEI), 3.28-3.63 (m, CH2,PEI+ CH2,PEG), 4.86 (bs, CH2,PEI+NHPEI); 13 C NMR (MeOD, (CHanthracene), 164.1 (CHanthracene), 176.1 (C=O); UV-vis (EtOH) λmax (nm): 256; Fluorescence: λex=390 nm, λem=359 nm. 123. (CHfluorene), 164.4 (CHfluorene), 173.3 (Cfluorene), 173.4 (Cfluorene), 176.1 (C=O); UV-vis (EtOH) λmax (nm): 205; Fluorescence: λex= 390nm, λem=357 nm.

  H NMR (MeOD): δ 0.92 (t, J=7.3 Hz, CH2,PEI), 1.14 (m, CH2,PEI), 1.19 (t, J=7.3 Hz, CH2,PEI), 1.27-1.36 (m, CH2,PEI+CH2,HB19), 1.91 (s, CH2,PEI), 2.18 (s, CH2,PEI), 2.21 (t, J=7.3 Hz, CH2,PEI), 2.37 (t, J=3.7Hz, CH2,PEI), 2.77-2.98 (m, CH2,PEI+CH2,HB19), 3.36 (bs, CH2,PEI), 3.50-3.67(m, CH2,PEI), 3.97-4.25 (m, CH2,PEI+NHPEI+N-CH3), 5.85-5.87 (m, N-CH2), 7.41-7.77 (m, Har+CHim), 8.58 (s, HB19).

M. Bouché, G. Dahm, A. Maisse-François, T. Achard, S. Bellemin-Laponnaz Eur. J.Inorg. Chem. 2016, 2828-2836

M. Bouché, G. Dahm, M. Wantz, S. Fournel, T. Achard, S.Bellemin-Laponnaz Dalton Trans 2016, 45, 11362-11368

Figure 60: Stability of 30nm PEI-AuNPs with serum

Acknowledgement

4) X-Ray diffraction

▪ [(NHC)PtI2(pyr)] complexes 5

Abbreviations

Acac Scheme 37: Selected NHC-Pt complexes for in vitro anticancer studies Among the tested NHC-Pt(II) derivatives, the three [(NHC)PtX2(pyridine)] complexes 1, 3 and 5 displayed greater cytotoxic activity than cisplatin as anticipated considering the effectiveness of NHC-Pt(II) combination already widely explored by our group, though the iodine complex is the most potent. The novel methyl-aminolevulinate functionalized precursor 49 has also been tested and shows IC50 values that favorably compare with the clinically used cisplatin. This compound is of interest for further application in photodynamic therapy, expecting to access a synergistic effect with the platinum centre. The four NHC-Pt(II) complexes were used as a reference to evaluate the possible benefit gained by oxidizing these well-established anticancer drugs into NHC-Pt(IV) prodrugs. We investigated here the combination of PEI with an epicocconone derivative presented in Scheme 49 which has been synthesized by the group of Dr X. Franck (IRCOF, Université de Rouen).

72.

Synthesized according to procedure G. Red solid, 10.9 mg, yield 99%. 1

Résumé

Bien que les agents anticancéreux à base de platine soient bien établis en clinique, plusieurs paramètres restent à optimiser, notamment leur toxicité et les phénomènes de résistances.

La combinaison platine-carbènes N-hétérocycliques (NHCs) a montré des résultats prometteurs dans la lutte antitumorale. Ainsi, afin de développer des agents anticancéreux innovants, ce travail résume les modifications structurales étudiées dans le but d'augmenter la cytotoxicité tout en réduisant les effets secondaires des complexes.

Une stratégie développée ici porte sur l'introduction de pnictogènes par échange de ligand pour observer un effet synergétique. Autrement, les efforts se sont concentrés sur les complexes de NHC-platine(IV) de leur synthèse à l'étude de leur stabilité, activité anticancéreuse et mécanisme d'action. Finalement, la combinaison des NHC-Pt à des nanotransporteurs a été étudiée afin d'améliorer leur biocompatibilité et sélectivité.

Mots clés :

Carbène N-hétérocyclique, Platine, Anticancer, Médecine Inorganique, Nanotransport

Résumé en anglais

Although platinum-based anticancer drugs are well established, several shortcomings have raised concerns, namely their toxicity and resistance mechanisms. Therefore, improved anticancer drugs are strongly awaited to substitute drugs currently used in clinics.

Remarkably, the combination of N-Heterocyclic Carbenes (NHCs) to platinum has recently demonstrated very promising results as anticancer agents. In the aim to access novel drugs, this work emphasizes several structural modifications to improve the cytotoxicity and lower side effects.

One strategy developed herein focus on the introduction of pnictogens by ligand exchange to access a synergistic effect. Otherwise, efforts mainly focused on NHC-platinum(IV) complexes from their synthesis to stability investigation and anticancer activities and mechanism of action. Finally, the combination of NHC-Pt drugs to nanodelivery devices has been investigated in order to improve both their biocompatibility and selectivity toward cancer cells.