Le but de ma thèse a été de concevoir des matériaux chimio-mécano répondants, des matériaux capables de permettre une transformation chimique réversible lorsqu’ils sont soumis à un stress mécanique. Tous les systèmes conçus ont été développés sur des substrats en silicone. Une première approche a consisté à créer des surfaces à sites cryptiques où une biotine est enfouie dans des brosses de chaines de poly(éthylène glycol). Le système streptavidine/biotine a été utilisé comme modèle. Ces surfaces sont anti-adsorbantes à la streptavidine sauf lorsqu’elles sont étirées à 50% où la biotine est reconnue mais les surfaces sont non réversibles. Dans une seconde approche, nous avons modifiés la surface du silicone par adsorption d’une multicouche de polyélectrolytes. Cette stratégie est basée sur la réticulation covalente du film par l’enzyme β-galactosidase modifiée. Nous sommes ainsi parvenus à créer une surface présentant une activité catalytique modulable par l’étirement mécanique, et ce, d’une façon partiellement réversible. Ce travail représente le premier exemple d’un système où une contrainte mécanique imposée à un matériau permet la déformation conformationnelle d’une enzyme et ainsi la diminution de l’activité catalytique. Dans une dernière approche, nous avons conçu un système mixte composé d’un substrat de silicone sur lequel un gel de polyacrylamide est greffée de façon covalente. Des enzymes ou des mécanophores pourront ainsi être inclus dans le réseau polymérique du gel de polyacrylamide et être étirés. Nous sommes parvenus à préparer de tels systèmes où l’hydrogel reste solidaire du film de silicone, sans apparition de craquelures jusqu’à 50%d’étirement. / The goal of my PhD was to develop new routes to design chemo-mechanoresponsive materials, materials that respond chemically to a mechanical stress, in a reversible way. All the systems designed during my PhD thesis were based on the functionalization of silicone sheets. First we created cryptic site surfaces by embedding biotin ligands into PEG brushes. The couple streptavidin/biotin was used as a model system. At rest, the surface so-prepared was antifouling and biotin ligands were specifically recognized by the streptavidin when the surface was stretched at 50%. Unfortunately, in this first approach, the mechanosensitive surface did not lead to a reversible process. In a second approach, we modified the silicone surface by using the polyelectrolyte multilayer (PEM) film deposition. This strategy was based on the covalent cross-linking of modified enzyme, the β-galactosidase, into the PEM. We succeeded in modulating the enzyme activity in the film under stretching and this approach appears as partially reversible under stretching/unstretching cycles. This work represents the first reported system where enzymatic activity can be modulated by stretching due to modulation of the enzyme conformation. In a last approach, we also designed a mixed system consisting of a silicone sheet onto which a polyacrylamide hydrogel is covalentlyattached with the goal to create a stretchable gel into which one can covalently attach enzymes or chemical mechanophores. These enzymes or mechanophores can thus be put under mechanical stress. We succeeded in creating a system that can be stretched up to 50% without detachment of the gel from the silicone and without inducing cracks in the gel.

Les biomatériaux de type hydrogel ou organogel obtenus à partir de molécules de faible masse molaire suscitent de plus en plus un vif intérêt autant sur le plan fondamental que sur le plan applicatif. Le travail, exposé ici, a pour objectif de synthétiser des composés amphiphiles présentant des variations de structure afin de pouvoir établir des relations entre la structure de ces composés et leurs propriétés gélifiantes. Nous avons été amenés à synthétiser des composés (bimodulaires et trimodulaires) avec et sans motif de jonction de type polyoxyéthylénique entre la partie peptidique et le module hydrophobe. Dans un deuxième temps, d?autres molécules amphiphiles gélifiantes ont été préparées, en substituant le motif polyoxyéthylénique par une entité dérivée du glycérol, pour permettre d'obtenir des composés d'origine renouvelable mais également pour diversifier la source de matières premières. Les composés visés ont été obtenus et leur comportement en solution a été étudié par différentes techniques (tensiométrie, conductimétrie, infrarouge,...). Certains d'entre eux, présentant des propriétés gélifiantes, associés aux sels de bore, ont été utilisés pour préserver le matériau bois (Pin Sylvestre). Les essais effectués se sont révélés concluant en termes de réduction du lessivage du bore car les tests avec Poria Placenta (champignon) cultivé sur un milieu gélosé ou avec les Réticulitermes Flavipès (termites) ont montré qu'un bois traité par l'association « borax-hydrogel » reste protégé même après lessivage / Biomaterials hydrogel or organogel obtained from low molecular weight molecules give rise to an increasing interest both in terms on the fundamental and application domain. The work outlined here, aims to synthesize amphiphilic compounds with structural changes in order to establish relationships between the structure of these compounds and their gelling properties. We were asked to synthesize compounds (bimodular and trimodular) with and without cause polyoxyethylene type junction between the peptide and the hydrophobic unit. In a second step, other gelling amphiphilic molecules were prepared by substituting the polyoxyethylene pattern derived by an entity glycerol, allowing to obtain compounds from renewable sources but also to diversify the source of raw materials. The target compounds were obtained and their behavior in solution has been studied by different techniques (tensiometry, conductivity, infrared,...). Some of them, with gelling properties, associated with boron salts have been used to preserve the wood material (Scots pine). The tests proved conclusive in terms of reducing the leaching of boron as tests with Poria placenta (mushroom) grown on an agar medium or with Reticulitermes flavipes (termite) showed that wood treated with the association "borax-hydrogel" is protected even after leaching

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Les assemblages colloïdaux représentent une nouvelle piste très prometteuse dans le domaine de l'ingénierie tissulaire. Idéalement, ce type d'assemblage permet l'obtention de matériaux injectables et gélifiants sur le site lésionnel, favorisant par la suite le développement de néo-tissus viables. Ce travail porte sur la formation de tels assemblages à base de chitosane et de poly(acide lactique) (PLA). Deux types d'assemblages ont été conçus et étudiés dans ce travail. Dans une première approche, le mélange de particules anioniques de poly (acide lactique) (PLA) avec du chitosane en solution faiblement acide conduit à la formation de « gels composites », résultant des interactions colloïde-polymère. Des analyses rhéologiques et de diffusion des rayons X aux petits angles ont permit de mettre en évidence le mode de formation et l'influence de plusieurs paramètres sur les propriétés finales de ces gels. Notamment, ils présentent des propriétés rhéofluidifiantes et un caractère réversible, c'est-à-dire que le gel peut se reformer après déstructuration mécanique. Le second type d'assemblage résulte du mélange de particules anioniques de PLA et de nanogels cationiques de chitosane, conduisant à la formation de « gels colloïdaux », par interactions colloïde-colloïde. L'influence de plusieurs facteurs sur la formation et les propriétés de ces gels a également été étudiée par mesures rhéologiques. Notre étude s'est notamment orientée sur la caractérisation et la stabilité des hydrogels physiques de chitosane sous forme colloïdale, ainsi que sur l'optimisation de leur cohésion / Colloidal assemblies may be a promising pathway to obtain injectable scaffolds favoring the development of neo-tissue in regenerative medicine. This work investigates the formation of such assemblies composed of chitosan, soluble or in suspension (nano-hydrogel), and poly(lactic acid) (PLA) nanoparticles. Two types of assemblies are studied. As a first approach, mixing negatively charged PLA particles and chitosan solution leads to the formation of “composite gels”, based on colloidpolymer interactions. Rheological and Small Angle X-Ray Scattering measurements highlighted the formation process and the influence of various parameters on final properties of these gels, which features shear-thinning and reversibility behavior, that is, the capacity to gel again after yielding. PLA nanoparticles could also be mixed with cationic chitosan nanoparticles, which are crosslinker free nano-hydrogels, leading to the formation of “colloidal gels”, based on colloid-colloid interactions. Influence of various parameters on gel synthesis and properties are investigated through rheological measurements. The study also focuses on the characterization and control of the morphological and cohesion properties of chitosan nanogel

Hydrogels are popular materials for biological applications since they exhibit properties like that of natural soft tissue and have tunable properties. Biodegradable hydrogels provide an added advantage in that they degrade in an aqueous environment thereby avoiding the need for removal after the useful lifetime. In this work, we investigated poly(β-amino ester) (PBAE) biodegradable hydrogel systems. To begin, the factors affecting the macromer synthesis procedure were studied to optimize the reproducibility of the resulting hydrogels made and create new methods of tuning the properties. Hydrogel behavior was then tuned by altering the hydrophilic/hydrophobic balance of the chemicals used in the synthesis to develop systems with linear and two-phase degradation profiles. The goal of the research was to better understand methods of controlling hydrogel properties to develop systems for several biomedical applications. Several systems with a range of properties were synthesized, and their in vitro behavior was characterized (degradation, mechanical properties, cellular response, etc.). From these studies, materials were chosen to serve as porogen materials and an outer matrix material to create a composite scaffold for tissue engineering. In most cases, a porous three dimensional scaffold is ideal for cellular growth and infiltration. In this work, a composite with a slow degrading outer matrix PBAE with fast degrading PBAE microparticles was created. First, a procedure for developing porogen particles of controlled size from a fast-degrading hydrogel material was developed. Porogen particles were then entrapped in the outer hydrogel matrix during polymerization. The resulting composite systems were degraded and the viability of these systems as tissue engineering scaffolds was studied. In a second area of work, two polymer systems, one PBAE hydrogel and one sol-gel material were altered through the addition of iron oxide nanoparticles to create materials with remote controlled properties. Iron oxide nanoparticles have the ability to heat in an alternating magnetic field due to the relaxation processes. The incorporation of these nanoscale heating sources into thermosensitive polymer systems allowed remote actuation of the physical properties. These materials would be ideal for use in applications where the system can be changed externally such as in remote controlled drug delivery.

Nous étudions les relations structure/propriétés d'hydrogels contenant des nanoparticules inorganiques. Les interactions spécifiques existant entre le poly(N,N-diméthylacrylamide) et des nanoparticules de silice sont à l'origine d'un fort renforcement mécanique des hydrogels, tant en termes de raideur que de résistance à la fracture. L'impact de l'introduction de nanoparticules de silice a été étudié d'un point de vue structural, thermodynamique et mécanique. Une étude détaillée des propriétés mécaniques des hydrogels hybrides à différentes échelles de temps a révélé une forte dépendance à la vitesse de sollicitation. Une modélisation du caractère viscoélastique de tels réseaux hybrides a été proposée et confrontée aux résultats expérimentaux, visant à décrire le comportement de ces doubles réseaux. Par ailleurs, une étude par techniques de diffusion de la lumière a été menée afin de caractériser la dynamique des nanoparticules de silice au sein des réseaux de polymère gonflés. Il a été démontré que le renforcement général des propriétés des hydrogels par les nanoparticules de silice est contrôlé par la dynamique de l'association PDMA/silice.

Chronic obstructive pulmonary disease (COPD) including emphysema is a devastating condition, increasing in prevalence in the US and worldwide. There remains no cure for COPD, rather only symptomatic treatments. Due to unique challenges of the lung, translation of therapies for acute lung injury to target chronic lung diseases like COPD has not been successful. We have been investigating lung derived extracellular matrix (ECM) hydrogels as a novel approach for delivery of cellular therapies to the pulmonary system. During the course of this work we have developed and characterized a lug derived ECM hydrogel that exhibits “injectability,” allowing cells or dugs to be delivered in a liquid and encapsulated at body temperature. The hydrogel self assembles in <5 minutes and achieves mechanical stiffness similar to other soft tissue ECM hydrogels. The hydrogel can support 3D cell growth and encapsulated cell viability. Encapsulated hMSCs can also still be activated by simulated inflammatory environments. Naïve mouse macrophages exposed to the fully formed gel were not significantly induced to express markers for pro or anti-inflammatory polarized phenotypes, but increased expression for several secreted inflammatory mediators was observed. We also investigated a novel approach for preparing and solubilizing the isolated ECM proteins, using digestion time as a variable for controlling hydrogel density (interconnectivity), mechanical stiffness, component protein size distribution, and cell behavior on fully formed gels. The potential future impact for the presented research includes optimization for future animal studies, expansion to additional applications, and the development of new derivative materials.

L’incidence des maladies cardiovasculaires d’origine athéromateuse demeure un problème majeur en santé publique et malgré le développement de techniques curatives endovasculaires, la chirurgie demeure nécessaire chez de nombreux patients. Le remplacement vasculaire se fait par une veine autologue qui reste le « gold standard » ou, lorsque les patients n’ont pas le capital vasculaire suffisant, par une prothèse. Actuellement, si les techniques utilisant des prothèses synthétiques sont satisfaisantes pour le remplacement d’artères de gros calibre, celui des artères de petit calibre demeure toujours un défi du fait du caractère thrombogène des biomatériaux utilisés et de leurs mauvaises propriétés mécaniques. Depuis quelques années, le concept d’ingénierie tissulaire a émergé et évolué. Il pourrait permettre de proposer de nouveaux types de substituts vasculaires hybrides et/ou biologiques, grâce en particulier à l’utilisation de cellules souches et de leurs progéniteurs, ouvrant d’intéressantes perspectives dans le domaine de l’ingénierie vasculaire. Le but de ce travail a été d’obtenir de manière fiable et reproductible des cellules à phénotype endothélial mature à partir de progéniteurs endothéliaux issus de moelle osseuse et sang périphérique humains et de définir leurs réponses dans des conditions proches de celles observées dans un vaisseau natif. Des cellules (PDECs : Progenitor Derived Endothelial Cells) ont pu être amplifiées à partir de progéniteurs, elles présentent les marqueurs membranaires classiquement utilisés pour définir des cellules endothéliales matures. Elles sont capables, sur différents revêtements utilisés cliniquement tels le collagène de type I et la colle de fibrine ainsi que sur un revêtement plus expérimental (Multicouches de PolyElectrolytes), de former une monocouche confluente. Ces PDECs résistent à des contraintes mécaniques de cisaillement de type artériel et l’analyse de gènes et protéines impliqués dans la biologie de l’endothélium a montré qu’elles répondent à ces stimulations par l’expression d’un phénotype en lien avec une activité antithrombogène. De plus, les travaux préliminaires réalisés sur ces PDECs cocultivés avec des progéniteurs ostéoblastiques, ouvrent d’intéressantes perspectives concernant leur utilisation dans le cadre de l’ingénierie du tissu osseux vascularisé. / The incidence of atherosclerotic arterial disease is still a major public health problem and despite endovascular surgery therapies, surgical treatment is necessary for many patients. Vascular bypass is performed with an autologous vein which remains the gold standard, or when patients do not have appropriate blood vessels to be used as replacement, with a synthetic prosthesis. Nowadays, synthetic vascular grafts have been successfully used in the treatment of the pathology of large arteries, but the replacement of the smaller sized arteries is still a challenge because synthetic vascular grafts are known to be highly thrombogenic and have poor mechanical properties. Recently, the tissue engineering concept has emerged and advances. It can allow to propose development of new hybrid or biologic vascular substitutes, using stem cells and progenitor cells, holding great promise for vascular tissue engineering. The aim of the present study was to obtain reliably and reproducibly, cells with mature endothelial phenotype from endothelial progenitor cells isolated from human bone marrow and peripheral blood and investigate cell response in conditions similar to those observed in a native vessel. We were able to expand cells (PDECs: Progenitor Derived Endothelial Cells) from progenitors which exhibit markers conventionally used to define mature endothelial cells. They were able, on scaffolds currently used in clinic like collagen type I and fibrin glue or on more experimental scaffold (Polyelectrolytes multilayers films), to form a confluent monolayer. These PDECs are able to withstand arterial shear stress and analysis of genes and proteins implicated in endothelium biology shows that these cells respond to shear stress stimulation with a phenotype connected to an anti-thrombogenic activity. Moreover, preliminary studies using co-cultures of PDECs and osteoblastic progenitors, open interesting perspectives concerning PDECs to be used in the field of vascularized bone tissue engineering.

De acordo com o conceito de sistemas de liberação controlada, o presente estudo foi baseado na utilização de polímeros hidrofílicos biocompatíveis, formadores de hidrogéis, para o desenvolvimento de matrizes na forma de filmes finos. Os polímeros utilizados para a formação das matrizes foram a quitosana proveniente das cascas de camarão, o amido de milho modificado e a poli(N-vinil-2-pirrolidona) - PVP. As matrizes foram reticuladas utilizando glutaraldeído. O fármaco escolhido para testar a capacidade de liberação dos dispositivos foi o anti-inflamatório não esteroidal (AINE) diclofenaco sódico. Para obtenção das matrizes com propriedades adequadas para essa finalidade, foram testadas misturas de quitosana-amido e quitosana-PVP. Após a triagem qualitativa, os dispositivos foram avaliados quanto à citotoxidade, intumescimento máximo, fração gel, parâmetros cinéticos associados à absorção de vapor de água e à capacidade de liberação de diclofenaco sódico in vitro. As formulações de quitosana-PVP foram as que apresentaram melhores propriedades para a aplicação proposta nesse estudo, se destacando a formulação A3, com alto percentual de liberação, boas propriedades de manuseio, poucos componentes na formulação diminuindo o potencial alergênico e aprovação no teste de citotoxicidade em células de camundongo (NCTC) pelo método de incorporação do vermelho neutro. / According to the concept of drug delivery systems, this study has based on the use of biocompatible hydrophilic polymers hydrogels-forming for the development of matrices in the form of thin films. The polymers used for forming the matrices were chitosan from shrimp shells, modified maize starch and poly(N-vinyl-2-pyrrolidone) PVP. The matrices were cross-linked using glutaraldehyde. The drug chosen to test the ability of the devices release was the non-steroidal anti-inflammatory drug (NSAID) sodium diclofenac. Mixtures between chitosan-starch and chitosan-PVP tested to obtain the matrices with suitable properties for this purpose. The devices after qualitative screening had evaluated for cytotoxicity, maximum swelling, gel fraction, kinetic parameters associated with absorbing water vapor and the release of diclofenac sodium able to in vitro. The formulations based on chitosan-PVP were the presents the best properties, in evidence formulation A3, with high percentage of delivery, good handing properties, few compounds/components reducing the allergenic potential and successful in vitro cell viability red uptake cytotoxicity assay, using cell culture mouse cells (NCTC).

Nenhuma / O processo sol-gel foi usado para nanoestruturar partículas de oxihidróxido de ferro e aprisiona-las na estrutura de micro-, meso- e macroporos + macroburacos (poros de dimensões micrométricas) da rede polimérica do PVA (álcool polivinílico). Esferas hidrogel de oxihidróxido de Fe-PVA com (3433 63 &#956;m) e sem (2833 69 &#956;m) macroburacos foram obtidas. Espectroscopia Mössbauer mostra que as esferas obtidas têm nanopartículas (majoritariamente &#8804;20 nm) de &#945;-Fe2O3, &#61543;-Fe2O3, &#945;-FeOOH e fases ainda superparamagnéticas a 20 K. As esferas hidrogel obtidas possuem elevada estabilidade química e boa rigidez mecânica. Capacidade adsortiva: 77,9 e 204,9 mgF/g, respectivamente para as esferas hidrogel sem (bom ajuste aos modelos de Langmuir e Freundlich) e com (bom ajuste ao modelo de Freundlich) macroburacos. Nos dois tipos de esferas, o mecanismo de quimissorção é predominante, mas o modelo de difusão intrapartícula sugere que o mecanismo de adsorção é mais complexo. Quatro ciclos de adsorção no modo coluna mostram uma pequena queda da eficiência de captura do F de 61,8 para 56,2%; neles, dessorção com solução NH3 min. 25% em peso mostra uma eficiência variando entre 95,8 e 98,8%. A estratégia de nanoestruturar as partículas de oxihidróxido de ferro e introduzir macroburacos na rede polimérica do PVA foi eficaz e realmente reforçou a captura do F. / The sol-gel process was used to nanostructure iron oxyhydroxide particles and to trap them into the structure of micro-, meso-, and macropores + macroholes (micrometer size pore) of the PVA (polyvinyl alcohol) polymeric network. Iron oxyhydroxide-PVA hydrogel spheres with (3433 63 microns) and without (2833 69 microns) macroholes were obtained. Mössbauer spectroscopy shows that the obtained spheres have nanoparticles (mainly &#8804;20 nm) of &#945;-Fe2O3, &#61543;-Fe2O3, &#945;-FeOOH, and phases still superparamagnetic at 20 K. The obtained hydrogel spheres have high chemical stability and good mechanical rigidity. Adsorptive capacity: 77.9 and 204.9 mgF/g, respectively for the hydrogel spheres without (fit well by the Langmuir and Freundlich models) and with (fit well by the Freundlich model) macroholes. In both types of spheres, the chemisorption mechanism is predominant, but the intraparticle diffusion model suggests that the adsorption mechanism is more complex. Four cycles of adsorption in the column mode show a small decrease of F capture efficiency from 61.8 to 56.2%; therein, desorption with NH3 solution min. 25 wt% shows an efficiency ranging between 95.8 and 98.8%. The strategy to nanostructure particles of iron oxyhydroxide and to introduce macroholes into the PVA polymer network was effective and really reinforced the F capture. Keywords: fluorine;