L’ingénierie des biomatériaux a connu un essor prodigieux ces dernières décennies passant de matériaux simples à des structures plus complexes, particulièrement dans le domaine cardiovasculaire. Cette évolution découle de la nécessité des biomatériaux de permettre la synergie de différentes propriétés, dépendantes de leurs fonctions, qui ne sont pas forcément toutes compatibles. Historiquement, les premiers matériaux utilisés dans la conception de dispositifs médicaux étaient ceux présentant le meilleur compromis entre les propriétés physico-chimiques, mécaniques et biologiques que nécessitait leur application. Cependant, il se peut que le dispositif possède les bonnes propriétés physico-chimiques ou mécaniques, mais que sa biocompatibilité soit insuffisante induisant ainsi des complications cliniques. Afin d’améliorer ces propriétés biologiques tout en conservant les propriétés de volume du matériau, une solution est d’en modifier la surface. L’utilisation d’un revêtement permet alors de moduler la réponse biologique à l’interface biomatériau-hôte et de diminuer les effets indésirables. Ces revêtements sont optimisés selon deux critères principaux : la réponse biologique et la réponse mécanique. Pour la réponse biologique, les deux approches principales sont de mettre au point des revêtements proactifs qui engendrent l’adhérence, laprolifération ou la migration cellulaire, ou passifs, qui, principalement, sont inertes et empêchent l’adhérence de composés biologiques. Des revêtements plus complexes utilisent les deux approches permettant l’adhérence spécifique de certainescellules tout en empêchant l’adhérence d’autres composants biologiques. Cette pratique est très utile pour lutter contre la resténose, complication survenant après opération de l’athérosclérose qui obstrue les vaisseaux sanguins. Une pratique courante est la pose d’un stent qui permet d’ouvrir l’artère de nouveau et de rétablir le flux sanguin. Le phénomène de resténose obstrue de nouveau le vaisseau sanguin, majoritairement par la prolifération incontrôlée de cellules musculaires lisses. La recherche sur les revêtements contre la resténose vise à inhiber la prolifération de ces cellules tout en facilitant la ré-endothélialisation. Les revêtements permettraient alors, à la fois de favoriser l’adhérence et la prolifération de cellules endothéliales et de limiter celles des cellules musculaires lisses à la surface du stent ou en limitant toute adhérence non-spécifique. Il a été démontré lors d’études précédentes qu’un copolymère à base de dextrane et de poly(méthacrylate debutyle) (PBMA) répondait à ces critères biologiques et qu’il possédait en plus une bonne résistance à la déformation, paramètre important lié à la déformation induite lors de l’implantation d’un stent. L’approche de ce projet était d’utiliser ce copolymère comme revêtement de stent et d’en améliorer la stabilité à long terme en formant des liens covalents avec le substrat. Pour ce faire, cela nécessitait l’activation de la partie dextrane du copolymère afin de pouvoir le greffer au substrat. Il était important de vérifier pour chaque étape l’influence des modifications effectuées sur les propriétés biologiques et mécaniques des matériaux obtenus, mais aussi d’un point de vue de la chimie, l’influence que cette modification pouvait induire sur la réaction decopolymérisation.... / The last decades have witnessed the remarkable growth of biomaterial science and engineering field, especiallyfor cardiovascular applications, for which devices have evolved from simple material to complex structures.This development has stemmed from the necessity for biomaterials to exhibit different properties, related totheir function, which are not always inherently compatible. Historically, the first materials selected for medicaldevices conception were the ones exhibiting the best compromise between all the physicochemical, mechanicaland biological requirements. Nevertheless, while physicochemical and mechanical properties are often handilycombined, the development of materials which also possess suitable biological properties have proved to bemuch more challenging, leading to clinical complications.Surface modification represents a valid solution to improve the biological performances of medical deviceswhile maintaining the bulk properties of the material. Biomaterial coatings may modulate the biologicalresponse at the biomaterial-host interface and decreases the undesirable effects. Coatings have been optimizedin regards to two main aspects: the biological response and the mechanical response. For the biologicalresponse, the two main approaches consist in 1) inducing cell adhesion, proliferation or migration with proactivecoatings and 2) using inert material, mostly, and avoiding the adhesion of any biological componentswith passive coatings.More complex coatings include the two approaches, allowing the adhesion of a specific type of cell whilerepelling other biological components adhesion. This method has been very useful against the restenosisphenomenon which obstructs blood vessels. A common practice is vessel stenting, a procedure that enables thereopening of the vessel and the restoration of the blood flow. Restenosis causes the new narrowing of the vessel,mostly due to uncontrolled smooth muscle cell proliferation. Researchers looked for coatings capable oflimiting the restenosis occurrence by inhibiting this cell proliferation along with facilitating the reendothelialization.Thus, the coatings would be able to improve endothelial cells adhesion and proliferation andto inhibit smooth muscle cells ones as well as avoiding non-specific adhesion.Previous studies showed that a copolymer made of dextran and poly(butyl methacrylate) (PBMA) demonstratedsuch biological properties and a good resistance to deformation, which is an important parameter related to thedeformation implied in a stent implantation. In this work, the approach was to use this copolymer as a stentcoating and to increase its long-term stability by providing covalent bonds with the substrate. To do so, thedextran part of the copolymer firstly needed to be activated in order to be grafted to the surface. Thus, it wasimportant to ascertain the influence of the multiple modifications on the biological and mechanical propertiesof the resulting materials at each step, but also towards a chemical point of view, the influence that thesemodifications may have on the subsequent copolymerization.

Surface modification techniques have played important roles in various aspects of modern technology. They have been employed to improve substrates by altering surface physicochemical properties. An ideal surface modifying technique would be a method that is applicable to any kind of materials prepared from a wide range of polymers and that can occur under mild reaction conditions. The work in this thesis has utilized four main concepts: I) the development of a ‘grafting-from’ technique by covalently growing polymer grafts from particle surfaces, II) the presence of steric and electrosteric forces due to long-range repulsive interactions between particles, III) a combined surface grafting and layer-by-layer approach to create polyelectrolyte multilayers (PEMs) on particle surfaces to fabricate strong and functional materials, and IV) the roles of hydrophilic polymer grafts and substrate geometry on surface degradation. A non-destructive surface grafting technique was developed and applied to polylactide (PLA) particle surfaces. Their successful modification was verified by observed changes to the surface chemistry, morphology and topography of the particles. To quantify the aggregation behavior of grafted and non-grafted particles, force interaction measurements were performed using colloidal probe atomic force microscopy (AFM). Long-range repulsive interactions were observed when symmetric systems, i.e., hydrophilic polymer grafts on two interacting surfaces, and asymmetric system were applied. Electrosteric forces were observed when the symmetric substrates interacted at pH 7.4. When PEMs were alternately assembled on the surface of poly(L-lactide) (PLLA) particles, the grafted surfaces played a dominated role in altering the surface chemistry and morphology of the particles. Three-dimensional scaffolds of surface grafted particle coated with PEMs demonstrated high mechanical performance that agreed well with the mechanical performance of cancellous bone. Nanomaterials were used to functionalize the scaffolds and further influence their physicochemical properties. For example, when magnetic nanoparticles were used to functionalize the scaffolds, a high electrical conductivity was imparted, which is important for bone tissue regeneration. Furthermore, the stability of the surface grafted particles was evaluated in phosphate buffered saline (PBS) solution. The nature of the hydrophilic polymer grafts and the geometry of the PLLA substrates played central roles in altering the surface properties of films and particles. After 10 days of PBS immersion, larger alterations in the surface morphology were observed on the film compared with microparticles grafted with poly(acrylic acid) (PAA). In contrast to the PAA-grafted substrates, the morphology of poly(acrylamide) (PAAm)-grafted substrates was not affected by PBS immersion. Additionally, PAAm-grafted microparticulate substrates encountered surface degradation more rapidly than PAAm-grafted film substrates. / <p>QC 20151002</p>

Cette thèse présente le développement de nanoparticules hybrides avec un coeur inorganique et une couronne organique pour des applications médicales. Des nanoparticules d’oxyde de fer ont été obtenues par synthèse polyol, en contrôlant leurs cristallinités, leurs morphologies (monocoeur ou multicoeur) et leurs tailles (de 4 à 37 nm). Leurs propriétés ont été évaluées et comparées pour de possibles applications théranostiques : en thérapie pour le traitement du cancer par hyperthermie magnétique, pour le diagnostic en tant qu’agents de contraste pour l’IRM. Les surfaces des nanoparticules ont été modifiées par greffage de polymères/polypeptides pour apporter de la stabilité en milieux biologiques et de nouvelles fonctionnalités. Le poly(éthylène glycol) (PEG) a été greffé pour ses propriétés de furtivité, le poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) et des polypeptides dérivés de l’élastine (ELPs) pour leurs propriétés thermosensibles, et la sonde fluorescente DY700 pour permettre le suivi des nanoparticules in vitro et in vivo. Les propriétés magnétiques et thermosensibles de ces nanoparticules coeur-couronne ont été étudiées avec un instrument unique combinant l’hyperthermie magnétique et un système de diffusion dynamique de la lumière. Ainsi, les variations de température, de diamètre et d’intensité diffusée ont pu être mesurées simultanément. Les propriétés de nanoparticules monocoeur et multicoeur greffées avec du PEG, et des nanoparticules monocoeur greffées avec un ELP contenant un peptide pénétrant ont d’abord été évaluées in vitro. Leurs internalisations dans des cellules de tumeur cérébrale humaine (glioblastome) ont permis d’étudier leurs cytotoxicités après traitement par hyperthermie magnétique, et ont montré une baisse de viabilité cellulaire jusqu’à 90 %. In vivo, l’injection intraveineuse de ces nanoparticules dans des souris a abouti à une accumulation dans les tumeurs. L’injection intratumorale suivie du traitement par hyperthermie magnétique a conduit à des élévations de température locales d’environ 10 °C, avec un effet significatif sur l’activité des tumeurs. / This thesis reports the development of hybrid nanoparticles made of an inorganic iron oxide core and an organic shell for medical applications. Iron oxide nanoparticles (IONPs) were produced by the polyol pathway, leading to a good control over their crystallinity and morphology (monocore or multicore). IONPs with diameters in the range of 4 to 37 nm were produced. Their properties as MRI contrast agents were assessed and compared, for possible theranostic applications. They can be used for treating cancer by magnetic hyperthermia, and as contrast agents for MR imaging. The surface of the IONPs was modified to bring stability in biological conditions, as well as new functionalities. Poly(ethylene glycol) was grafted for its stealth property, poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) and elastin-like polypeptides (ELPs) for their thermosensitive capabilities, and a DY700 fluorescent probe was grafted for tracking nanoparticles in vitro and in vivo. The magnetic and thermosensitive properties of the nanoparticles were studied using a unique set-up combining magnetic hyperthermia with dynamic-light scattering. This set-up allowed measuring the elevations of temperature of the samples as well as variations in diameter and backscattered intensity. Monocore and multicore IONPs grafted with PEG, and monore IONPs grafted with a diblock ELP were tested in vitro. Their interactions with glioblastoma cells were studied, from the internalization pathway inside the cells to their cytotoxic effect (up to 90 %) under magnetic hyperthermia. In vivo, nanoparticles intravenously injected in mice accumulated in the tumors. Intratumoral administration followed by magnetic hyperthermia treatment led to elevations of temperature of up to 10 °C, with a significant effect on the tumor activity.

The design of biomaterials, historically initiated and developed by physicians and engineers, in the last decades has slowly shifted toward a more biochemical based approach. For the replacement, repair and regeneration of tissues scientists are now focusing on materials that stimulate specific biological response at the molecular level. These biomaterials have already shown interesting applications in cell proliferation, differentiation, and extracellular matrix production and organization when the material modifications are designed to elicit specific interactions with cell integrins. In the present work we propose the application of this strategy for the development of blood-compatible materials. We first identified, in the coagulation cascade a key enzyme that constitute a valuable biological target for the development of anti-thrombogenic compounds. Piperazinyl-amide derivatives of N-alfa-(3-trifluoromethyl-benzenesulfonyl)-L-arginine were synthesized as graftable thrombin inhibitors. These inhibitors provided a spacer arm for surface grafting and a fluorine tag for XPS (X-ray photoelectron spectroscopy) detection. The possible disturbance of biological activity due to a variable spacer-arm fixed on the N-4 piperazinyl position was evaluated in vitro against human alfa-thrombin, in silico by molecular modelling and via X-ray diffraction study. Selected inhibitors, having inhibition potency in the mM range, were grafted on polyesters surface via wet chemistry and photochemical activation treatments. Wet chemistry surface grafting was performed by specific hydroxyl chain-ends activation and resulted in bioactive molecules fixation of 20-300pmol/cm2. The photochemical grafting was performed using a molecular clip providing an aromatic azide, for nitrene insertion into a polymer, and an activated ester for grafting of tag compounds. This grafting technique resulted in a dramatic increase in fixed bioactive signals (up to nmol/cm2). The material blood-compatibilization induced by the surface fixation of the inhibitors, was measured by a static blood clot weight measurement test. The wet chemistry grafting technique resulted in moderate blood-compatibilization while by the photochemical grafting method important decrease in surface blood clot formation was observed. In the latter case, the blood response to material contact was found to be strongly affected by the polyester surface photo-degradation induced by the activation treatment.

The design of biomaterials, historically initiated and developed by physicians and engineers, in the last decades has slowly shifted toward a more biochemical based approach. For the replacement, repair and regeneration of tissues scientists are now focusing on materials that stimulate specific biological response at the molecular level. These biomaterials have already shown interesting applications in cell proliferation, differentiation, and extracellular matrix production and organization when the material modifications are designed to elicit specific interactions with cell integrins. In the present work we propose the application of this strategy for the development of blood-compatible materials. We first identified, in the coagulation cascade a key enzyme that constitute a valuable biological target for the development of anti-thrombogenic compounds. Piperazinyl-amide derivatives of N-alfa-(3-trifluoromethyl-benzenesulfonyl)-L-arginine were synthesized as graftable thrombin inhibitors. These inhibitors provided a spacer arm for surface grafting and a fluorine tag for XPS (X-ray photoelectron spectroscopy) detection. The possible disturbance of biological activity due to a variable spacer-arm fixed on the N-4 piperazinyl position was evaluated in vitro against human alfa-thrombin, in silico by molecular modelling and via X-ray diffraction study. Selected inhibitors, having inhibition potency in the mM range, were grafted on polyesters surface via wet chemistry and photochemical activation treatments. Wet chemistry surface grafting was performed by specific hydroxyl chain-ends activation and resulted in bioactive molecules fixation of 20-300pmol/cm2. The photochemical grafting was performed using a molecular clip providing an aromatic azide, for nitrene insertion into a polymer, and an activated ester for grafting of tag compounds. This grafting technique resulted in a dramatic increase in fixed bioactive signals (up to nmol/cm2). The material blood-compatibilization induced by the surface fixation of the inhibitors, was measured by a static blood clot weight measurement test. The wet chemistry grafting technique resulted in moderate blood-compatibilization while by the photochemical grafting method important decrease in surface blood clot formation was observed. In the latter case, the blood response to material contact was found to be strongly affected by the polyester surface photo-degradation induced by the activation treatment.

Les élastomères chargés sont des matériaux nanocomposites présentant un compromis de propriétés unique exploité notamment dans les bandes de roulement des pneumatiques. Ils comprennent une charge renforçante, silice ou noir de carbone, qui doit présenter un module élevé, des dimensions nanométriques, et avoir la capacité de se disperser et de former des liaisons fortes avec la matrice. La nanocellulose est caractérisée par une morphologie anisotrope avec une section de l’ordre de 10 nm, et une structure cristalline avec un module d’environ 150 GPa. L’objectif de la thèse est d’évaluer si ce substrat peut être employé comme charge renforçante. Les travaux se divisent ainsi en trois parties portant successivement sur l’obtention d’aérogels de haute surface spécifique, la modification de leur surface, puis leur emploi comme renfort. La mise au point d’un protocole de lyophilisation de suspensions de nanocellulose, et d’un procédé d’estérification par voie gaz des aérogels obtenus, a permis d’obtenir des charges avec une haute surface spécifique et une interface avec un agent hydrophobe ou un agent de couplage. Une attention particulière a été accordée à la topochimie de la réaction dont le suivi a été réalisée par RMN du solide. Ces charges ont ensuite été incorporées au sein d’un élastomère, puis les matériaux obtenus ont été caractérisés par MET et par des tests mécaniques. Dans le cas d’un aérogel de nanocellulose avec une haute surface spécifique et un agent de couplage, les propriétés des matériaux obtenus sont alors caractéristiques du comportement d’un élastomère chargé. / Filled elastomers are nanocomposites with specific properties that make them suitable for numerous applications including tyre gum. They include a reinforcing filler, silica or carbon black, with features like a high elastic modulus, a size in the nanometer range, and the ability to be dispersed and to perform strong interactions with the matrix. Nanocellulose is an anisotropic nanoparticule with a crystalline structure whose elastic modulus is estimated around 150 GPa. The goal of this project is to study its ability to be a reinforcing filler. The work is divided into three parts dealing respectively with high specific surface aerogel preparation, their surface modification, and their use as a filler. A specific freeze drying protocol and a specially designed gas phase esterification process were used in order to obtain fillers with a high specific surface and an interface that can be either covered by an hydrophobic or a coupling graft. A special care has been devoted to the topochemistry, which has been monitored all along the reaction thanks to solid state NMR. These fillers have then been introduced in elastomers, the resulting materials being characterized by TEM and mechanical tests. In the case of a high specific surface nanocellulose aerogel with an interface covered by coupling agent, material features appeared then to be typical of filled elastomers.