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Hyaline cartilage is a highly specialized tissue, which plays an important role in the articulating joints of an individual. It provides the joints with a nearly frictionless, impact resisting surface to protect the ends of the articulating bones. Articular cartilage has a poor self-repair capacity and, therefore, it rarely heals back to normal after an injury. Overweight, injuries, overloading and genetic factors may initiate a degenerative disease of the joint called osteoarthritis. Osteoarthiritis is a major global public health issue. Currently, the most used treatment for large articular cartilage defects is joint replacement surgery. However, possibilities to replace this highly invasive operation with strategies based on tissue engineering are currently investigated. The idea of the tissue engineering is to optimize the use of the cells, biomaterials and culture conditions to regenerate a new functional tissue for the defect site. The goal of this thesis was to manufacture cartilage tissue in cell culture conditions in vitro. Bovine primary chondrocytes isolated from the femoral condyles were used in all the experiments for neocartilage production. The samples were collected for histology, gene expression level quantifications, and analyses of proteoglycan (PG) content and quality. The histological sections were stained for type II collagen and PGs, the quantitative RT-PCR was used to observe the relative expressions of aggrecan, Sox9, procollagen α2(I) and procollagen α1(II) genes. The PGs were quantified using a spectrophotometric method, and agarose gel electrophoresis was used to separate the PGs according to their size. In the two first studies, we optimized the culture conditions of in vitro scaffold-free culture technique to produce the native-type hyaline cartilage of a good quality. We found out that high glucose concentration and hypertonic medium at 20% oxygen tension promoted the best hyaline-like neocartilage tissue production. Glucosamine sulfate supplementation, low oxygen tension, 5 mM glucose concentration and a transient TGF-β3 supplementation were not beneficial for the neocartilage formation in the scaffold-free cell culture system. In the third study, we used these newly defined, optimized culture conditions to produce the neocartilage tissues in the HyStem™ and the HydroMatrix™ scaffold materials and we compared these tissues to the ones grown as scaffold-free control cultures. We noticed that there was no difference between the controls and the scaffolds, and occasionally the scaffold-free controls had produced better quality cartilage than the ones with the scaffolds. Overall, the neocartilage tissues were of good hyaline-like quality in the third study. Their extracellular matrix contents were close to the native cartilage, although the neotissues lacked the zonal organization typical to the normal articular cartilage. The tissues had the right components, but their ultrastructure differed from the native cartilage. In conclusion, we were able to optimize our in vitro neocartilage culture method further, and discovered a good combination of the culture conditions to produce hyaline-like cartilage of good quality. Surprisingly, the scaffold materials were not beneficial for the cartilage formation. / Lasi- eli hyaliinirusto on pitkälle erikoistunutta kudosta, jolla on erittäin tärkeä rooli yksilön nivelten toiminnassa. Kudos suojaa ruston alapuolista luuta muodostamalla lähes kitkattoman ja joustavan liikkumista helpottavan pinnan. Lasiruston oma uusiutumiskyky on hyvin heikko, ja näin ollen kudos vain harvoin paranee alkuperäisen kaltaiseksi vaurion jälkeen. Ylipaino, vammat, liiallinen kuormitus tai geneettiset tekijät voivat käynnistää rustokudoksen rappeutumisen. Tätä tilaa kutsutaan nivelrikoksi. Nivelrikko on valtava kansanterveydellinen ongelma. Keinonivelleikkaus on nykyisellään ainoa hoitokeino pinta-alaltaan laajojen nivelruston vaurioiden hoitoon. Vaihtoehtoja tämän suuren ja invasiivisen kirurgisen operaation korvaamiseksi tutkitaan kuitenkin koko ajan ympäri maailmaa. Kudosteknologian ajatuksena on optimoida solujen, biomateriaalien ja erilaisten kasvatusolosuhteiden käyttö uuden, alkuperäisen kaltaisen toiminnallisen kudoksen luomiseksi vauriokohtaan. Väitöskirjan kaikissa kolmessa osatutkimuksessa uudisrustokudoksia tuotettiin käyttäen naudan polven rustosta eristettyjä primäärisiä rustosoluja. Näytteet kerättiin histologisia analyysejä, geenin ilmentymistutkimuksia ja proteoglykaanisisällön ja -jakauman (PG) analyyseja varten. Histologisista leikkeistä värjättiin tyypin II kollageeni ja PG:t, ja kvantitatiivista RT-PCR -menetelmää käytettiin aggrekaani-, Sox9-, prokollageeni α2(I)- ja prokollageeni α1(II)-geenien suhteellisten ilmentymistasojen määrittämiseen. Proteoglykaanisisältö analysoitiin käyttäen spektrofotometristä menetelmää, ja PG:t eroteltiin kokonsa perusteella agaroosigeelielektroforeesia käyttäen. Kahdessa ensimmäisessä osatutkimuksessa optimoitiin tukirakenteetta kasvattujen uudisrustojen kasvatusolosuhteita natiivin kaltaisen lasiruston tuottamiseksi. Havaitsimme, että korkea glukoosipitoisuus ja hypertoninen elatusaine yhdistettynä 20 % happiosapaineeseen tuotti parhaimman laatuista uudisrustokudosta tutkituista yhdistelmistä. Glukosamiinisulfaatin lisäys, matala happiosapaine, 5 mM glukoosi konsentraatio tai TGF-β3:n lisääminen alkuvaiheessa eivät edesauttaneet uudisrustokudosten muodostumisessa. Kolmannessa osatutkimuksessa otettiin käyttöön uudet, hyväksi havaitut kasvatusolosuhteet yhdistettynä HyStem™ and HydroMatrix™ -tukimateriaaleihin, ja niitä verrattiin tukirakenteettomaan kasvatusmenetelmään. Tutkimuksessa havaittiin, ettei tukirakenteettoman kontrollin tai tukimateriaalien välillä ollut mitään eroa, ja että kontrollikasvatukset tuottivat ajoittain jopa parempaa rustoa kuin tukimateriaalein kasvatetut. Kaiken kaikkiaan kaikki tuotetut uudiskudokset muistuttivat laadullisesti lasiruston kaltaista kudosta. Molekyylisisältö lähenteli natiivia rustoa, vaikkakin uudiskudoksista puuttui normaalille nivelrustolle tyypillinen vyöhykkeinen järjestäytyminen. Kudoksissa oli parhaimmillaan oikea määrä oikeita komponentteja, mutta ne eivät vain olleet järjestäytyneet oikealla tavalla. Onnistuimme optimoimaan uudisrustokudosten kasvatusmenetelmäämme. Löysimme hyvän kasvatusolosuhteiden yhdistelmän, jonka avulla kykenimme tuottamaan lasiruston kaltaista uudisrustokudosta. Hivenen yllättäenkin, tukimateriaalit eivät olleet avuksi tutkimuksessamme uudisrustokudoksia muodostettaessa.

Le contrôle de la morphologie de la couche active en optoélectronique organique représente un objectif majeur du fait de son impact sur la stabilité et les performances des dispositifs. En particulier, le degré d'autoorganisation d'un mélange de deux composés à caractère donneur (D) et accepteur (A) d’électrons, ainsi que leurs orientations sont déterminants pour obtenir à la fois un de transfert de charges efficace et des chemins de percolation continus jusqu'aux électrodes. Durant ce travail de thèse, nous avons synthétisé plusieurs séries de co-oligomères à blocs donneur-accepteur capables de s’auto-organiser pour former des lamelles alternées D/A à longue distance. Les co-oligomères présentent une architecture moléculaire de type diade (DA) ou triade (DAD ou ADA), et sont constitués d’une longueur de bloc D variable. Les molécules sont toutes composées d'un bloc A à base de perylène diimide et d'un bloc D contenant les motifs thiophène, fluorène et benzothiadiazole. Une attention particulière a été portée sur l'étude des propriétés optiques, électrochimiques, photophysiques, structurales ou encore opto-électroniques de nos matériaux. En particulier, nous nous avons montré que l’organisation lamellaire était très fortement dépendante de l’architecture moléculaire, puisque seuls les systèmes AD et ADA conduisent à une structuration à longue distance. Par ailleurs, en ajustant la densité électronique au sein du bloc D, nous avons montré qu’il était possible de contrôler à la fois le temps de formation et la durée de vie des états à transfert de charges. Enfin,les premiers résultats de caractérisation du transport de charges et des propriétés photovoltaïques démontrent l’intérêt de ces matériaux dans la réalisation de dispositifs photovoltaïques organiques mono-composants. / In the field of organic opto-electronics, the good control of the active layer morphology in devices represents a major objective to improve the stability and the photovoltaic performances. Especially when blends of selforganizing electron donor (D) and acceptor (A) moieties are combined, their mutual orientation and the degree of supramolecular ordering are determinant in controlling the fundamental energy, the electron transfer processes and the existence of continuous percolation pathways for charge carriers. In this work, we have designed and synthesized different series of donor-acceptor block co-oligomers able toself-assemble in a lamellar structure at very long range. The co-oligomers are made of a dyad (AD) or triad (DAD, or ADA) molecular architecture, and have a variable length of the D block. The A block is constituted of a perylene diimide unit, and the D block of benzothiadiazole, thiophene and fluorene segments. A particular attention was paid on the studies of optical, electrochemical, photophysical, structural and opto-electronical properties. In particular, we showed that the lamellar organization was strongly dependent on the molecular architecture, since only the AD and ADA systems lead to long-range organization. Moreover, by tuning the electronic density along the D block, it has been possible to control both the formation and lifetime of the charge transfer states. Finally, the first results on charge transport and photovoltaic properties demonstrate the high interest of these materials for the elaboration of single component organic photovoltaic devices.

The intervertebral disc (IVD), situated between adjoining vertebrae, consists of the gelatinous nucleus pulposus (NP) in the centre surrounded by the tougher annulus fibrosus (AF). Its main roles are to distribute loads and to act as joints. With aging, degenerative disc disease (DDD) occurs due to an imbalance in anabolic and catabolic events in the IVD, which results in a loss of function. Lower back pain (LBP) affects 84% of people at some point in their lifetime and is strongly associated with DDD. Current LBP treatments have limited long term efficacy and are symptomatic rather than curative. Cell-based therapies are regarded to hold great potential for the treatment of DDD as it has been hypothesised that they could regenerate the damaged tissue and alleviate LBP. A number of natural and synthetic biomaterials have been investigated as NP tissue engineering scaffolds with varying results. In this study, a self assembling peptide hydrogel (SAPH) was investigated for its potential as a cell carrier and/or scaffold for NP tissue engineering. SAPHs display the advantages of natural polymer hydrogels such as biocompatibility and biodegradability whilst combining the advantages of synthetic materials such as controlled structural and mechanical propertiesCharacterisation determined that the SAPH nanofibrous architecture had features that were of similar scale to extracellular matrix (ECM) components of the human NP. The mechanical properties of the SAPH could be optimised to closely match the native tissue. The system could shear thin and self-heal making the system ideally suited to delivery via minimally invasive procedure. The three dimensional (3D) culture of bovine NP cells (bNPCs) in the SAPH demonstrated that the NP phenotype could be restored after de-differentiation during monolayer culture. Gene expression results demonstrated that ‘traditional’ and ‘novel’ NP markers were highly expressed throughout in vitro culture. Cell viability was high, cell population remained stable and bNPCs adopted the characteristic rounded morphology of native NPCs. Finally, type II collagen and aggrecan, the main ECM components of the NP, were deposited with increasing production over culture period. Growth differentiation factor 6 (GDF-6) has been identified as the most promising current growth factor for inducing discogenic differentiation from human bone marrow mesenchymal stem cell (h-BMMSCs). After samples were stimulated with GDF-6, gene expression results confirmed that a NP-like phenotype could be induced with high expression of ‘traditional’ and ‘novel’ NP markers. Cell viability was high, cell population remained stable and NP associated ECM components were deposited with cells displaying a rounded morphology. Interestingly, when h-BMMSCs were cultured without GDF-6, it was strongly suggested that spontaneous discogenic differentiation occurred after culture in the SAPHs as ‘traditional’ and ‘novel’ NP markers were highly expressed, morphology was comparable to native NPCs and type II collagen and aggrecan were deposited extracellularly. If these findings were accurate then this is the first study to demonstrate that a NP-like phenotype could be induced from MSCs without use of an exogenous growth factor or a discogenic bioactive motif. Despite exciting and novel results, further work is required to confirm the potential of SAPHs for NP tissue engineering scaffolds.

Ce travail de thèse propose de réaliser un nanofil électrique auto-assemblé constitué de protéines. L'unité de base de ce nanofil est une protéine chimère comprenant un domaine capable de former des fibres amyloïdes (Het-s 218-289) et un domaine capable d'effectuer des transferts d'électrons (une rubrédoxine). Le premier domaine permet la réalisation d'une fibre par auto-assemblage tandis que le deuxième est exposé à la surface de cette structure. Les caractéristiques redox du domaine exposé permettent aux électrons de se déplacer d'un bout à l'autre de la fibre par sauts successifs. Un tel nanofil a été créé et caractérisé par différentes techniques biophysiques. Ensuite, la preuve de la conduction des nanofils a été apportée sur des ensembles d'objets, de manière indirecte par électrochimie, et de manière directe par des mesures tension/courant. Ces travaux ouvrent la voie à la réalisation d'objets biocompatibles, biodégradables, possédant des propriétés électroniques exploitables dans des dispositifs technologiques. / The research described in this thesis aims at creating a self-assembled nanowire only made of proteins. The building block of this wire is a chimeric protein that comprises an amyloid fibril forming domain (Het-s 218-289) and an electron transfer domain (rubredoxin). The first one self-assembles in amyloid fibrils which display the second at their surface. Redox characteristics of the exposed domain allow electrons to move from one extremity of the fibril to the other by successive jumps. Such a nanowire has been created and characterized by various biophysical experiments. Then, the conductivity of the nanowires has been demonstrated on sets of wires by electrochemistry and by direct current measurements. These experiments pave the way for future design of biocompatible and biodegradable objects that possess usable electronic properties.

This doctoral thesis is dedicated to the synthesis and characterization of novel functionalized hybrid structures for biomedical purposes. Systems reported in this work can be subdivided into the two main groups: natural-based materials and synthetic amphiphilic block copolymers. Both groups were studied as perspective theranostic agents for medical applications. In the first group, natural polysaccharides glycogen and mannan were selected as starting materials for preparation of novel nanoconjugates that possess ability for multimodal detection in vivo. Because grafting of natural macromolecules with synthetic polymers generally slows down the biodegradation rate, both polysaccharides were modified in two different ways to form nanoprobes with or without poly(2-methyl-2-oxazoline)s chains. The prepared nanoconjugates were functionalized with N-hydroxysuccinimide-activated fluorescence and magnetic resonance imaging labels. The resulting materials were tested both in vitro and in vivo and were shown to be completely biocompatible, biodegradable and exhibit some extra benefits in terms of their practical usage in biomedicine. Glycogen was functionalized with allyl and propargyl groups with following freeze-drying from aqueous solutions to form nano- and microfibrous materials. The presence of both...

A mixed self assembling monolayer (mSAM) chip with attached heparin was developed to analyze heparin-protein interactions using a Reichert Inc, SR7000, surface plasmon resonance (SPR) instrument. The heparin was attached via streptavidin-biotin linkage where the streptavidin was covalently coupled to the mSAM and biotinylated heparin bound to it. These chips were then used to quantify the interactions of fibroblast growth factor-2 (FGF-2) with the surface bound heparin. Kinetic rate constants of association and disassociation were calculated. The association data of FGF-2 with heparin was fit to a single compartment, well-mixed model as the data did not exhibit mass transfer limitations. The results suggested that rebinding was prevalent and observed disassociation rates differed significantly in the presence of competing soluble heparin during disassociation. Our results indicate that the Reichert instrument and mSAM chips can be used to analyze heparin-protein interactions but that a careful protocol, outlined in this thesis, should be followed to obtain optimal data. / Master of Science

Réalisé en cotutelle, sous la direction du Pr. Bernold Hasenknopf, à l'Institut Parisien de Chimie Moléculaire, Université Pierre et Marie Curie (Paris VI, France) et dans le cadre de l'Ecole Doctorale "Physique et Chimie des Matériaux" - Spécialité Chimie Inorganique (ED397). / Notre projet se situe dans le contexte actuel de recherche d’énergies « propres », qui permettraient d’assurer un développement durable. Nous nous sommes intéressés à l’édification de systèmes moléculaires bio-inspirés, capables de : (i) collecter efficacement l’énergie solaire, grâce au design d’assemblages supramoléculaires multi-nucléaires photoactifs ; (ii) transférer efficacement l’énergie accumulée jusqu’au catalyseur, lequel effectue les processus multiélectroniques nécessaires à la génération des combustibles. Notre choix s’est porté sur les systèmes hybrides covalents inorganiques-organiques, à base de polyoxométallates (POMs) photoactivés, dans le visible, par des complexes de métaux de transition. Dans un premier temps, nous avons étudié des chromophores dinucléaires de Ru(II) comprenant le motif électroattracteur 1,3,5-triazine, en raison de leurs capacités de transfert d’énergie et pour la prolongation du temps de vie de l’état excité du chromophore. Dans un deuxième temps, la nécessité d’établir une connexion covalente entre le complexe métallique et le POM nous a amené à faire le design de ligands polydentates ditopiques de type trialkoxo. Cette méthodologie, flexible sur le plan synthétique, nous a donné accès à une famille de POMs présentant des sites de coordination de denticité variable (de monodentate à tridentate), en vue d’accommoder divers cations métalliques. Nous avons ensuite étudié la complexation de divers métaux de transition sur ces nouveaux POMs. Les systèmes visés étaient soit des systèmes à transfert de charges photoinduits (complexation de Ru, de Re), soit des systèmes photocatalytiques (complexation de Re et Co) et/ou électrocatalytiques (complexation de Co). L’auto-assemblage des POMs, guidé par le mode de coordination du métal (tel Pd(II) ou Re(I)) et la géométrie de la brique constituante POM, a été également étudié, car il constitue un outil puissant dans l’assemblage de systèmes supramoléculaires multi-nucléaires photoactifs. Les systèmes visés sont destinés à servir de systèmes modèles dans l’édification de systèmes moléculaires à composants multiples et de matériaux hybrides multi-fonctionnels. / We are interested in the photocatalytic production of clean energy sources, such as H2, in order to ensure global sustainable development. We focused our attention on molecular bio-inspired systems, capable of : (i) efficient light harvesting, based on the careful design of multi-nuclear supramolecular photoactive units; (ii) efficient energy transfer to the catalyst, chosen for its ability to perform multi-electronic processes needed in fuels production. We chose inorganic-organic covalent hybrids, constituted of visible-photoactivated POMs by transition metal complexes. First, we designed and studied Ru(II) dinuclear complexes, based on the electrodeficient motif 1,3,5-triazine, for their energy transfer properties and extended excited-state lifetimes. Then, the covalent connection, to ensure between sub-units, compelled us to design new ditopic polydentate ligands. This flexible synthetic methodology gave access to a family of POMs presenting various types of coordination sites (from monodentate to tridentate), in order to allow complexation of different metals. Complexation studies on the new POMs were conducted and aimed at : (i) photoinduced charge transfer systems (complexation of Ru, and Re) ; (ii) photocatalytic (complexation of Re and Co) and/or electrocatalytic systems (complexation of Co). Metal-directed self-assembling of POMs (guided by Pd(II) or Re(I)) and the coordination geometry of the POMs building-block, has also been studied, as a tool in the building-up of electro- and photoactive supramolecular systems. The model systems studied will be used to design molecular multi-functional hybrid materials.

En aquesta Tesi, un nou biomaterial de disseny composat per seqüències peptídiques repetitives i amfifíliques, que per autoensamblatge forma xarxes de nanofibres (i hidrogels), AcN-RADARADARADARADA-CONH2, s´ha utilitzat com a anàleg de la matriu extracel·lular per al manteniment, proliferació i diferenciació cel·lular. Aquest pèptid s'ha funcionalititzat amb motius biològicament actius procedents de proteïnes de la matriu extracel·lular incloent laminina-1 i colàgen IV. El scaffold peptídic autoensamblant RAD16-I i els seus derivats biològicament actius s´han caracteritzat i provat utilitzant diferents sistemes cel·lulars com pot ser les cèl·lules d'aorta humanes (HAEC), hepatocits madurs i la línea progenitora de fetge (Lig-8). La proteòlisi d'aquest pèptid s'ha avaluat utilitzant tripsina com a enzim proteolític, i els fragments resultants s'han analitzat per MALDI-TOF i AFM. Així mateix, la segona generació de biomaterials basats en el RAD16-I s'ha provat tant amb HAEC com amb hepatocits madurs. Amb aquests sistemes hem demostrat que el desenvolupament d'una matriu biomiètica reforça, a la vegada que manté, les funcions específiques de cada teixit. En particular, els resultats obtinguts en diferenciació, proliferació i manteniment de la funció cel·lular utilitzant pèptids sintètics autoensamblants són comparables amb els resultats que s'obtenen utilitzant matrius biològiques (Colàgen I i Matrigel). Això indica que els nostres anàlegs de la matriu extracel·lular poden substituir als materials naturals, i suggereix l'ús d'aquests materials intel·ligents amb capacitat instructiva en aplicacions terapèutiques. Així mateix s'ha provat que l'ús d'aquests pèptids auto-ensamblants és eficient en la construcció d'un nínxol de cèl·lules mare. Hem sigut capaços de controlar la cinètica cel·lular (de simètrica a assimètrica) induint diferenciació funcional, a la vegada que es mantenia una petita proporció de cèl·lules no diferenciades. Aquests resultats indiquen clarament que hem sigue capaços d'obtenir un nínxol on cèl·lules primitives (Lig-8) es diferencien adquirint funcions d'hepatocits madurs. Hem desenvolupat una plataforma de biomaterials que es podrien utilitzar per la funcionalització amb innumerables biomolècules amb capacitat d'induir processos biològics com la diferenciació, proliferació i funció metabòlica. Aquests biomaterials, preveiem que tindran un gran impacte a l'àrea terapèutica i biología regenerativa. / En esta Tesis, un nuevo biomaterial de diseño compuesto por secuencias peptídicas repetitivas y amfifílicas que por autoensamblaje forma redes de nanofibras (e hidrogeles), AcN-RADARADARADARADA-CONH2 (RAD16-I), se ha utilizado como análogo de la matriz extracelular para el mantenimiento, proliferación y diferenciación celular. Este péptido se ha funcionalizado con motivos biológicamente activos procedentes de proteínas de la matriz extracelular incluyendo laminina-1 y colágeno IV. El scaffold peptídico autoensamblante RAD16-I y sus derivados biológicamente activos se han caracterizado y probado utilizando diferentes sistemas celulares como puede ser células endoteliales de aorta humanas (HAEC), hepatocitos maduros y la línea progenitora de hígado Lig-8. La proteólisis de este péptido se ha evaluado utilizando tripsina como enzima proteolítico, y los fragmentos resultantes se han analizado por MALDI-TOF y AFM. Asimismo, la segunda generación de biomateriales basados en el RAD16-I se ha probado tanto con HAEC como hepatocitos maduros. Con estos sistemas hemos demostrado que el desarrollo de una matriz biomimética refuerza a la vez que mantiene las funciones específicas de cada tejido. En particular, los resultados obtenidos en diferenciación, proliferación y mantenimiento de la función celular utilizando los péptidos sintéticos auto-ensamblantes son comparables con los resultados que se obtienen usando matrices biológicas (Colágeno I y Matrigel). Esto indica que nuestros análogos de la matriz extracelular pueden reemplazar a los materiales naturales, y sugiere el uso de estos materiales inteligentes con capacidad instructiva en aplicaciones terapéuticas. Asimismo, se ha probado que el uso de estos péptidos auto-ensamblantes es eficiente en la construcción de un nicho de células madre. Hemos sido capaces de controlar la cinética celular (de simétrica a asimétrica) induciendo diferenciación funcional, a la vez que se mantenía una pequeña proporción de células no diferenciadas. Estos resultados indican claramente que hemos sido capaces de obtener un nicho donde células primitivas (Lig-8) se diferencian adquiriendo funciones de hepatocitos maduros. Hemos desarrollado una plataforma de biomateriales que se podrían utilizar para la funcionalización con innumerables biomoléculas con capacidad de inducir procesos biológicos como la diferenciación, proliferación y función metabólica. Estos biomateriales preveemos que tendrán un gran impacto en el área terapéutica y biología regenerativa. / In this Thesis, a new designed biomaterial made out of short repetitive amphiphilic peptide sequence AcN-RADARADARADARADA-CONH2 (RAD16-I) that self-assembles forming nanofiber networks (hydrogel scaffold) has been used as synthetic extracellular matrix analog for cell maintenance, proliferation and differentiation. This peptide has been functionalized with biological active motifs from extracellular matrix proteins including laminin-1 and collagen IV. The prototypic self-assembling peptide scaffold RAD16-I and its biologically active derivatives have been characterized and tested using several cellular systems such as human aortic endothelial cells (HAEC), mature hepatocytes and a putative liver progenitor cell line, Lig-8. The proteolysis of the peptide RAD16-I has been evaluated using trypsin as a proteolytic enzyme and the resulting fragments have been analyzed by MALDI-TOF and AFM. Moreover the second generation of RAD16-I-based biomaterials have been tested using HAEC and mature hepatocytes. With these systems we have shown that the development of a biomimetic matrix enhances as well as maintain tissue-specific functions. In particular, the results obtained in cell differentiation, proliferation and maintenance of cell function using the synthetic self-assembling peptide matrices, are comparable with the results obtained using natural biological matrices counterparts (Collagen-I and Matrigel). This indicates that our extracellular matrix analogs can replace the use of naturally-derived materials and suggests the use of these smart biomaterials with instructive capacity for cells in therapeutics. Moreover, the use of the self-assembling peptide RAD16-I in the recreation of a stem-cell niche proved to be highly efficient. We were able to control stem-cell kinetics (from symmetric to assymetric) inducing functional differentiation while maintaining a small proportion of undifferentiated cells. This striking results clearly indicate that we were able to obtain a stem-cell niche where primitive cells (Lig-8) undergo differentiation acquiring mature hepatic functions. We have developed a biomaterial platform that can be used for functionalization with innumerable biomolecules, with capacity to induce biological processes like differentiation, control of proliferation, metabolic function, etc. These biomaterials will have a strong impact in therapeutics and regenerative biology.

Notre projet se situe dans le contexte actuel de recherche d’énergies « propres », qui permettraient d’assurer un développement durable. Nous nous sommes intéressés à l’édification de systèmes moléculaires bio-inspirés, capables de : (i) collecter efficacement l’énergie solaire, grâce au design d’assemblages supramoléculaires multi-nucléaires photoactifs ; (ii) transférer efficacement l’énergie accumulée jusqu’au catalyseur, lequel effectue les processus multiélectroniques nécessaires à la génération des combustibles. Notre choix s’est porté sur les systèmes hybrides covalents inorganiques-organiques, à base de polyoxométallates (POMs) photoactivés, dans le visible, par des complexes de métaux de transition. Dans un premier temps, nous avons étudié des chromophores dinucléaires de Ru(II) comprenant le motif électroattracteur 1,3,5-triazine, en raison de leurs capacités de transfert d’énergie et pour la prolongation du temps de vie de l’état excité du chromophore. Dans un deuxième temps, la nécessité d’établir une connexion covalente entre le complexe métallique et le POM nous a amené à faire le design de ligands polydentates ditopiques de type trialkoxo. Cette méthodologie, flexible sur le plan synthétique, nous a donné accès à une famille de POMs présentant des sites de coordination de denticité variable (de monodentate à tridentate), en vue d’accommoder divers cations métalliques. Nous avons ensuite étudié la complexation de divers métaux de transition sur ces nouveaux POMs. Les systèmes visés étaient soit des systèmes à transfert de charges photoinduits (complexation de Ru, de Re), soit des systèmes photocatalytiques (complexation de Re et Co) et/ou électrocatalytiques (complexation de Co). L’auto-assemblage des POMs, guidé par le mode de coordination du métal (tel Pd(II) ou Re(I)) et la géométrie de la brique constituante POM, a été également étudié, car il constitue un outil puissant dans l’assemblage de systèmes supramoléculaires multi-nucléaires photoactifs. Les systèmes visés sont destinés à servir de systèmes modèles dans l’édification de systèmes moléculaires à composants multiples et de matériaux hybrides multi-fonctionnels. / We are interested in the photocatalytic production of clean energy sources, such as H2, in order to ensure global sustainable development. We focused our attention on molecular bio-inspired systems, capable of : (i) efficient light harvesting, based on the careful design of multi-nuclear supramolecular photoactive units; (ii) efficient energy transfer to the catalyst, chosen for its ability to perform multi-electronic processes needed in fuels production. We chose inorganic-organic covalent hybrids, constituted of visible-photoactivated POMs by transition metal complexes. First, we designed and studied Ru(II) dinuclear complexes, based on the electrodeficient motif 1,3,5-triazine, for their energy transfer properties and extended excited-state lifetimes. Then, the covalent connection, to ensure between sub-units, compelled us to design new ditopic polydentate ligands. This flexible synthetic methodology gave access to a family of POMs presenting various types of coordination sites (from monodentate to tridentate), in order to allow complexation of different metals. Complexation studies on the new POMs were conducted and aimed at : (i) photoinduced charge transfer systems (complexation of Ru, and Re) ; (ii) photocatalytic (complexation of Re and Co) and/or electrocatalytic systems (complexation of Co). Metal-directed self-assembling of POMs (guided by Pd(II) or Re(I)) and the coordination geometry of the POMs building-block, has also been studied, as a tool in the building-up of electro- and photoactive supramolecular systems. The model systems studied will be used to design molecular multi-functional hybrid materials. / Réalisé en cotutelle, sous la direction du Pr. Bernold Hasenknopf, à l'Institut Parisien de Chimie Moléculaire, Université Pierre et Marie Curie (Paris VI, France) et dans le cadre de l'Ecole Doctorale "Physique et Chimie des Matériaux" - Spécialité Chimie Inorganique (ED397).