Membrane technology has been actively used as a separation tool in the chemical, environmental, and biopharmaceutical industries for several decades. As membrane quality requirement in the industry has increased, efforts have been directed towards enhancement in mechanical strength, chemical durability and functionality of membranes. One of the approaches for membrane quality enhancement is based on the combination of hydrogel technology with membrane technology. This thesis focused on the application and development of hydrogel based membranes, notably hydrophilized PVDF (polyvinylidene fluoride) membrane for hydrophobic interaction membrane chromatography; the fabrication of paper-hydrogel composite membranes for membrane chromatography; development of a technique for coating alginate (a natural hydrogel) on the outer surface of a hollow fiber membrane for potential application in bioreactors and the use of hollow fiber membranes as mold for fabrication calcium alginate fibers for biomedical and tissue engineering applications. A membrane chromatography-based polishing technique was developed for removing leached protein-A and aggregates from monoclonal antibody (mAb). A commercial synthetic membrane that is known to be hydrophilized by hydrogel grafting was employed to develop this polishing process that resulted in highly pure mAb, free from aggregates and protein-A. This mAb polishing technique could easily be integrated with a hydrophobic interaction membrane chromatography based mAb purification process. A paper-hydrogel composite membrane was developed as an inexpensive alternative to commercial synthetic membranes used for carrying hydrophobic interaction membrane chromatography. Poly(N-vinylcaprolactam) or PVCL hydrogel was coated on Whatman filter paper to prepare these membranes. These environment responsive membrane which responded to changes in salt concentration, gave excellent fractionation of multi-component protein mixtures. As case study, a mixture of immunoglobulin G, human serum albumin and insulin was fractionated. A technique for modifying the surface of synthetic hollow fiber membranes with alginate (a natural hydrogel) was developed. This manner of surface modification led to the improvement in membrane mass transport. The alginate was cross-linked on the outer surface of the membrane by diffusion of the cross-linker (calcium ions) through the membrane pores. The calcium alginate coating layer was characterized by optical and transmission electron microscopy, contact angle measurement, hydraulic permeability measurement and by examining solute transport. Hollow and solid calcium alginate fibers were fabricated using a novel hollow fiber membrane based moulding technique. The pore present on the hollow fiber membrane served as the reservoir for the calcium chloride solution with cross-linked the alginate within the lumen. The calcium alginate fibers produced were characterized by optical, transmission electron, and scanning electron microscopy. Cell immobilization experiments were carried out to demonstrate biocompatibility and potential for tissue engineering applications. / Thesis / Doctor of Philosophy (PhD)

Interpenetrating polymer networks (IPN’s) consist of two overlapping cross-linked networks that are not bonded to each other. Hydrogel IPN’s are of application interest due to properties such as mechanical reinforcement, modulated drug release and biodegradation kinetics, dual polymer activities in vivo, and novel nanostructured morphologies. Prior IPN hydrogels reported in the literature either required surgical implantation (disadvantageous for several reasons) or were polymerized in situ (limited to a small subset of biologically safe chemistries). Alternatively, we formed IPN’s using a mixing injector to deliver orthogonally reactive functionalized prepolymer solutions that gel upon contact. Specifically, we use hydrazone chemistry to gel a thermosensitive poly(N-isopropylacrylamide) (PNIPAM) network and kinetically orthogonal thiosuccinimide or disulfide chemistry to cross-link a second network of hydrophilic poly(vinylpyrrolidone) (PVP). The resulting IPN’s preserve the thermoresponsive properties of the PNIPAM constituent but exhibit slower, smaller, and more reversible transitions due to entanglement with the highly hydrophilic PVP network (potentially useful to reduce the problem of burst release in thermoresponsive drug delivery systems). Mechanical reinforcement was evidenced by the increased shear storage modulus of IPN composites relative to the sum of the individual component moduli, particularly so in IPN’s employing the thiosuccinimide-cross-linked PVP. The nanostructure of the IPN hydrogels was further studied using small angle neutron scattering with contrast matching, and was found to combine features characteristic to each single network component (PNIPAM-rich static domains embedded in PVP-rich fractal clusters). However, our results suggest some slight changes to their scattering profiles, indicative of partial mixing or influence of each network structure upon the other. Corroborating investigations with single-molecule super-resolution fluorescence microscopy, operating at a slightly larger length scale, show the formation of separate populations of mixed and individual domains or clusters of each polymer type. These properties suggest such injectable IPN’s for further investigation as prospective biomaterials. / Thesis / Doctor of Philosophy (PhD) / This thesis describes the development of overlapping but unconnected polymer networks formed by mixing of completely injectable polymer precursors. The interlocking pair of networks is based on one component that shrinks upon heating and the other component that offers the potential for biological adhesion. Entanglement between the two components renders them mutually reinforcing and changes the shrinking and reswelling behaviour of the temperature-responsive component. The structure of the composite network is also distinctive from either individual component, forming alternating, unevenly mixed regions richer in one or the other component. The composite’s properties are attractive for a potential bioadhesive drug delivery carrier and, in the future, a possible wound closure biomaterial.

The development of easily fabricated, highly stable DNA-based microarray and continuous flow concentrating devices is vital for several biomedical and environmental applications. Nucleic acid biosensors can be used for genetic analysis, disease diagnosis, drug discovery, food and water quality control and more, however methods of fabrication are tedious, and the longevity of sensors is compromised by the fragility of the sensing component. In this report, the fabrication and characterization of two biosensing modalities – microarrays and microgels – composed of Rolling Circle Amplification (RCA) product in poly(oligoethylene glycol methacrylate) (POEGMA) hydrogels are investigated. RCA product microarrays were developed by the sequential printing of aldehyde and hydrazide functionalized POEGMA precursors on nitrocellulose paper, exploiting rapid gelling via hydrazone crosslinking to generate thin film hydrogel sensing arrays. POEGMA/RCA product microgels for affinity column applications were synthesized using an inverse emulsion polymerization technique. Inkjet printing evenly deposited RCA product in all wells, with POEGMA effectively stabilizing DNA on the cellulose substrate. Hybridization of complementary probe to the encapsulated RCA product was optimized, yielding a signal to noise ratio of ~4 for a large range of probe concentrations. Microgels were successfully synthesized in the size range of 10-60 μm diameter, and a linear model that can accurately predict size based on initiator and emulsifier concentration was developed. The encapsulation efficiency of RCA product in different sized microgels was explored, with larger microgels entrapping more product and the highest encapsulation efficiency calculated at 56%. These results demonstrate that POEGMA hydrogels can be utilized to encapsulate and stabilize RCA product in two distinct structures, providing a basis for the development of easily fabricated biosensors for more specific applications. / Thesis / Master of Applied Science (MASc)

The objective of this thesis was the synthesis and characterisation of two linear multifunctional PEG-alternatives for bioconjugation and hydrogel formation: i) Hydrophilic acrylate based copolymers containing peptide binding units and ii) hydrophilic polyether based copolymers containing different functional groups for a physical crosslinking. In section 3.1 the successful synthesis of water soluble and linear acrylate based polymers containing oligo(ethylene glycol) methyl ether acrylate with either linear thioester functional 2-hydroxyethyl acrylate, thiolactone acrylamide, or vinyl azlactone via the living radical polymerisation technique Reversible Addition Fragmentation Chain Transfer (RAFT) and via free-radical polymerisation is described. The obtained polymers were characterized via GPC, 1H NMR, IR and RAMAN spectroscopy. The RAFT end group was found to be difficult to remove from these short polymer chains and accordingly underwent the undesired side reaction aminolysis with the peptide during the conjugation studies. Besides that, polymers without RAFT end groups did not show any binding of the peptide at the thioester groups, which can be improved in future by using higher reactant concentrations and higher amount of binding units at the polymer. Polymers containing the highly reactive azlactone group showed a peptide binding of 19 %, but unfortunately this function also underwent spontaneous hydrolysis before the peptide could even be bound. In all cases, oligo(ethylene glycol) methyl ether acrylate was used with a relatively high molecular weight (Mn = 480 Da) was used, which eventually was efficiently shielding the introduced binding units from the added peptide. In future, a shorter monomer with Mn = 300 Da or less or hydrophilic N,N’-dialkyl acrylamide based polymers with less steric hindrance could be used to improve this bioconjugation system. Additionally, the amount of monomers containing peptide binding units in the polymer can be increased and have an additional spacer to achieve higher loading efficiency. The water soluble, linear and short polyether based polymers, so called polyglycidols, were successfully synthesized and modified as described in section 3.2. The obtained polymers were characterized using GPC, 1H NMR, 31P{1H} NMR, IR, and RAMAN spectroscopy. The allyl groups which were present up to 20 % were used for radical induced thiol-ene chemistry for the introduction of functional groups intended for the formation of the physically crosslinking hydrogels. For the positively charged polymers, first a chloride group had to be introduced for the subsequent nucleophilic substitution with the imidazolium compound. There, degrees of modifications were found in the range 40-97 % due to the repulsion forces of the charges, decreased concentration of active chloride groups, and limiting solution concentrations of the polymer for this reaction. For the negatively charged polymers, first a protected phosphonamide moiety was introduced with a deprotection step afterwards showing 100 % conversion for all reactions. Preliminary hydrogel tests did not show a formation of a three-dimensional network of the polymer chains which was attributed to the short backbone length of the used polymers, but the gained knowledge about the synthetic routes for the modification of the polymer was successfully transferred to longer linear polyglycidols. The same applies to the introduction of electron rich and electron poor compounds showing π-π stacking interactions by UV-vis spectroscopy. Finally, long linear polyglycidyl ethers were synthesised successfully up to molecular weights of Mn ~ 30 kDa in section 3.3, which was also proven by GPC, 1H NMR, IR and RAMAN spectroscopy. This applies to the homopolymerisation of ethoxyethyl glycidyl ether, allyl glycidyl ether and their copolymerisation with an amount of the allyl compound ~ 10 %. Attempts for higher molecular weights up to 100 kDa showed an uncontrolled polymerisation behaviour and eventually can be improved in future by choosing a lower initiation temperature. Also, the allyl side groups were modified via radical induced thiol-ene chemistry to obtain positively charged functionalities via imidazolium moieties (85 %) and negatively charged functionalities via phosphonamide moieties (100 %) with quantitative degree of modifications. Hydrogel tests have still shown a remaining solution by using long linear polyglycidols carrying negative charges with long/short linear polyglycidols carrying positive charges. The addition of calcium chloride led to a precipitate of the polymer instead of a three-dimensional network formation representing a too high concentration of ions and therefore shielding water molecules with prevention from dissolving the polymer. These systems can be improved by tuning the polymers structure like longer polymer chains, longer spacer between polymer backbone and charge, and higher amount of functional groups. The objective of the thesis was partly reached containing detailed investigated synthetic routes for the design and characterisation of functional polymers which could be used in future with improvements for bioconjugation and hydrogel formation tests. / Das Ziel dieser Arbeit war es zwei lineare multifunktionale PEG-Alternativen für die Bioconjugation und Hydrogelbildung herzustellen und zu charakterisieren: i) Wasserlösliche Acrylat-basierte Copolymere mit Peptidbindungseinheiten und ii) wasserlösliche Polyether-basierte Copolymere mit verschiedenen funktionalen Gruppen für eine physikalische Vernetzung. In Abschnitt 3.1 wurde die erfolgreiche Synthese von wasserlöslichen und linearen Acrylat-basierten Polymeren, die Oligo(ethylen glycol) methyl ether acrylat mit jeweils 2-Hydroxyethyl acrylate modifiziert mit linearem Thioester, Thiolactonacrylamid und Vinylazlacton enthielten, mittels der lebenden Polymerisationstechnik Reversible Additions-Fragmentierungs Kettenübertragung (RAFT) und mittels freier radikalischer Polymerisation durch GPC, 1H NMR, IR und RAMAN Spektroskopie bewiesen. Es erwies sich als schwer die RAFT-Endgruppe von den kurzen Polymerketten zu entfernen und führte zur Nebenreaktion Aminolyse mit dem Peptid während des Konjugationsprozesses. Außerdem zeigten Polymere ohne RAFT-Endgruppen keine Peptidbindung an den Thioestergruppen, was durch höhere Konzentration der Reaktanten und größeren Anteil an Peptidbindungseinheiten am Polymer in Zukunft verbessert werden könnte. Polymere mit Azlaktongruppen zeigten eine Bindung von 19 %, wobei dies eine sehr reaktive Gruppe ist und vor der Peptidbindung noch hydrolysieren kann. In allen Fällen wurde Oligo(ethylen glycol) methyl ether acrylat mit Mn = 480 Da verwendet, welches die Peptidbindungsstellen abschirmen kann. Daher können in Zukunft Monomere mit Mn = 300 Da oder N,N’-Dialkylacrylamid-basierte Monomere mit weniger sterischer Hinderung für dieses System verwendet werden. Zusätzlich kann der Anteil an Monomeren mit Peptidbindungseinheiten im Polymer und zusätzlicher Seitenkette erhöht werden, um höhere Bindungseffektivitäten zu erreichen. Die erfolgreiche Synthese und Modifikation von wasserlöslichen, linearen und kurzen Polyether-basierten Polymeren, sogenannten Polyglycidolen, konnte in Abschnitt 3.2 mittels GPC, 1H NMR, 31P{1H} NMR, IR und RAMAN Spektroskopie bewiesen werden. Die Allylgruppe, die bis zu 20 % vorhanden war, wurde für die radikalisch induzierte Thiol-En Chemie zur Einführung von funktionellen Gruppen verwendet. Für die positiv geladenen Polymere, wurde zuerst eine Chloridgruppe generiert, die anschließend für die nukleophile Substitution mit einer Imidazolkomponente verwendet wurde. Dabei wurden Substitutionsgrade von 40-97 % gefunden, was an den Abstoßungskräften der Ladungen, verringerter Konzentration der aktiven Chloridgruppen und der begrenzten Löslichkeitskonzentration bei dieser Reaktion liegt. Für die negativ geladenen Polymere wurde zuerst eine geschützte Phosphonamidgruppe eingeführt, die anschließend entschützt wurde und bei allen Reaktionen einen Umsatz von 100 % zeigte. Vorläufige Hydrogeltests zeigten keine Bildung eines dreidimensionales Netzwerks der Polymerketten aber es wurden Erkenntnisse über die synthetischen Routen für die Modifikation der Polymere für den Transfer auf lange lineare Polyglycidole gewonnen. Das gleiche gilt für die Einführung von elektronreichen und elektronarmen Komponenten, die eine π-π Stapelwechselwirkung mittels UV-vis Spektroskopie zeigte. Letztlich wurden lange lineare Polyglycidole bis zu Molmassen von Mn ~ 30 kDa erfolgreich in Abschnitt 3.3 hergestellt und mittels GPC, 1H NMR, IR and RAMAN Spektroskopie bewiesen. Dies gilt für die Homopolymerisation von Ethoxyethyl glycidyl ether, Ally glycidyl ether und deren Copolymerisation mit einem Anteil der Allylkomponente von ~ 10 %. Versuche um höhere Molekulargewichte bis zu 100 kDa zeigten ein unkontrolliertes Polymerisationsverhalten, welches durch eine niedrigere Initiierungstemperatur weiter verbessert werden kann. Ebenso wurden die Allylseitengruppen mittels radikalisch induzierter Thiol-En Chemie modifiziert, um positivgeladene Funktionalitäten durch Imidazolgruppen (85 %) und negativgeladene Funktionalitäten durch Phosphonamidgruppen (100 %) in quantitativen Umsätzen einzuführen. Hydrogeltests von langen linearen Polyglycidolen, die negativ geladene Gruppen haben, mit langen/kurzen linearen Polyglycidolen, die positiv geladene Gruppen haben, haben eine verbleibende Lösung gezeigt. Die Zugabe von Calciumchlorid führte zum Ausfall des Polymers anstatt zu einem dreidimensionalen Netzwerk repräsentiert durch eine zu hohe Ionenkonzentration. Dies führte zu einer Abschirmung der Wassermoleküle vom Polymer und verhinderte, dies aufzulösen. Das System kann verbessert werden, indem die Polymerstruktur variiert wird, z.B. durch längere Polymerketten, größere Abstände zwischen Polymerhauptkette und Ladung und einen größeren Anteil an funktionellen Gruppen. Das Ziel der Arbeit wurde teilweise erreicht, welches detailliert untersuchte Syntheserouten für das Design und die Charakterisierung von funktionellen Polymeren beinhaltet, welche in Zukunft mit Verbesserungen für Bioconjuations- und Hydrogelformulierungstests verwendet werden können.

Osteoarthritis is the most prevalent musculoskeletal disease in humans, severely reducing the standard of living of millions of people. Osteoarthritis is characterized by degeneration and loss of articular cartilage which leads to pain, and loss of joint motility and function. Individuals suffering from severe osteoarthritis are commonly treated with full knee replacements. The procedure does eliminate the problem of degrading cartilage tissue; however, it does not fully restore function and its lifetime can be limited. To overcome the disadvantages of current treatments, tissue engineering has become a focus of research to regenerate cartilage. Tissue engineering attempts to repair or replace damaged tissue with cells, biomaterials, and/or molecular signals. Biodegradable scaffolds serve as a temporary replacement for the tissue until it has regenerated. Two types of scaffolds that have been used in tissue engineering are electrospun scaffolds and hydrogels. We have proposed and fabricated a scaffold for cartilage tissue engineering that incorporates an electrospun cylinder and a thermosetting hydrogel in order to provide improved properties compared to either individual material. Electrospun cylinders were created by sintering electrospun mats that include salt pores. The addition of salt pores decreased the mechanical properties of the electrospun materials while also improving the capability of cells to infiltrate into the scaffold. The sintering process involved the connecting of one electrospun mat to an adjacent one. Specifically, poly(d,l-lactide) was capable of sintering to an adjacent electrospun mat when exposed to either heat (near the glass transition temperature) or tetrahydrofuran vapor. The sintering process did not deteriorate the structure or function of the electrospun material. Sintering allowed the creation of unique structures of electrospun material that previously could not be produced. A thermosetting hydrogel was added to the scaffold to replicate the function of proteoglycans present in articular cartilage. A composite scaffold of electrospun polymer and hydrogel showed improved mechanical properties and better integration of the scaffold in vivo compared to an electrospun scaffold with no hydrogel. In conclusion, the composite electrospun and hydrogel scaffold could become an excellent tissue engineering scaffold to treat patients suffering from osteoarthritis. / Ph. D.

L’embolisation thérapeutique est devenu le traitement de choix pour l’hémorragie, les malformations artériovéneuses ou certains types de cancer. Parmi différents agents d’embolisation,les microsphères non dégradables (Embozene®, Bead BlockTM,…) sont les plus utilisées. Leur forme bien sphérique et leur taille calibrée permettent un meilleur ciblage dans les vaisseaux et une bonne qualité de l’occlusion. Dans certains cas cliniques, l’embolisation temporaire, envisageable avec l’utilisation des microsphères résorbables peut être bénéfique pour les patients. Le but du travail réalisé au cours de cette thèse a été le développement de microsphères résorbables satisfaisant les différents critères pour être employées comme matériaux d’embolisation (taille calibrée,biocompatibles, élastique pour être injectée au travers des cathéters mais suffisamment rigide pour résister à la pression sanguine). Dans cet objectif, nous avons développé une méthode de synthèse de microsphères constituées d’hydrogels hydrolysables par polymérisation en suspension. Une large gamme de microsphères ont été synthétisées en modulant la nature du réticulant et/ou la composition des milieux de polymérisation. Les expériences in vitro ont démontré que les microsphères obtenues sont satisfaisantes pour permettre leur injection au travers des cathéters. La dégradation rapide des ponts de réticulation a été confirmée à travers la diminution du module élastique G’ et du pH du surnageant, accompagnée d’une augmentation du taux de gonflement.Malgré une dégradation partielle des microsphères (due à une réaction secondaire formant des liaisons de réticulation non dégradables), le temps de l’hydrolyse a répondu parfaitement au cahier de charges (entre 7 et 49 jours). Des études complémentaires pour optimiser la réaction de polymérisation vont permettre le développement de microsphères totalement dégradables. / Therapeutic embolization is nowadays a first line treatment for haemorrhage, arteriovenous malformation or tumors. Among different embolization agents, non degradable microspheres(Embozene®, Bead BlockTM,…) are the most employed thanks to their well calibrated spherical shape which allows good occlusion. In some cases including treatment of uterine fibroids or chemo-sensitive tumors, it may be interesting to achieve a temporary embolization to avoid definitive destruction of the tissue. Temporary embolization would be possible using biodegradable microspheres. The aim of our work was to develop degradable microspheres having all requiredcharacteristics to be used as embolization material (well calibrated in size, biocompatible, rigide enough to resist blood pressure but elastic enough to remain intact during injection through catheter). To this purpose, we have developed hydrolysable hydrogel based microspheres by suspension polymerization. A wide range of microspheres was synthesized by varying the type of crosslinker and composition of the polymerization medium. In vitro test showed that the microspheres have suitable characteristics to pass through catheter. Degradation studies revealed a rapid diminution of G’ modulus and the pH of the supernatants, accompanied by an increase of swelling ratio due to the hydrolysis of the crosslinkings. Although microspheres were not totally degradable as expected (since a side reaction had created non degradable crosslinking during the polymerisation), characterisations showed promising results that the degradation did occur within a suitable time scale requirements for temporal embolization.

Cette thèse porte sur l’étude de la cavitation, c’est-à-dire l’apparition d’une bulle dans un liquide soumis à une dépression. Le contrôle du processus est d’un grand intérêt dans plusieurs domaines, de l’hydrodynamique à la biologie. En fait ce phénomène, apparemment inoffensif, peut provoquer des graves dommages comme la fracture d’hélices ou la mort d’arbres. La première partie de la thèse se focalise sur la cavitation dans un système biomimétique. Il s’agit de micro-volumes d’eau encapsulés dans un milieu poro-élastique. L’évaporation de l’eau à travers l’hydrogel génère des pressions négatives et finalement l’apparition d’une bulle. Lorsque la première bulle de cavitation apparait dans une cellule, elle peut déclencher en quelques microsecondes l’apparition d’autres bulles dans les cellules voisines, en amorçant un effet d’avalanche ultra-rapide. Nous résolvons la dynamique et l’acoustique des bulles, dans le cas des événements uniques ou multiples. La réalisation d’un dispositif innovant ou les volumes du liquide sont encapsulés entre l’hydrogel et une lame de verre ouvre la voie à l’investigation de l’eau métastable. Une deuxième partie du travail a été consacrée à une étude interdisciplinaire où la microfluifique et la biologie sont combinées et appliqués à la livraison de médicament. Le dispositif est composé d’un vaisseau sanguin artificiel en communication avec un tissu cible placé dans un compartiment créé exprès. Les parois du canal microfluidique sont tapissées de cellules endothéliales pour reproduire la paroi réelle d’un vaisseau sanguin in vivo. Ce dispositif permet l’étude des effets des bulles activées par des ultrasons sur la barrière endothéliale. / The present thesis focuses on cavitation process, meaning nucleation and dynamics of a bubble within a liquid as a result of pressure decrease. In particular, we investigate the growth of the vapor phase in micrometric volumes of water confined by a poro-elastic material. In systems where water is encapsulated in a porous medium, molecules can evaporate from the pores resulting in a remarkable pressure reduction and bubbles nucleation. Once a vapor bubble nucleates, it can trigger within few microseconds the appearance of other bubbles in the neighbor cavities, activating an ultra-fast avalanche-like phenomenon. We resolved the dynamics and acoustics of cavitation bubbles, in case of singles or multiple nucleation events. The realization of an innovative device where water is encapsulated between a porous material and a glass window opens the way for metastable water investigation. A second part of the manuscript is devoted to a new project where microfluidics and biology are combined and applied to drug delivery. The device consists of an artificial blood vessel in communication with the target tissue accommodated in a purposely designed compartment (tissue-on-a-chip). The walls of the microfluidic channel mimicking the vessel are lined with endothelial cells to reproduce the actual walls of in vivo blood vessels. This device allows to investigate the effects of ultrasound-activated bubbles on the blood vessels wall.

Ce travail de thèse est principalement axé sur la création d'un nouveau réacteur biocompatible permettant l'encapsulation et l'étude de bactéries électroactives. Ce compartiment de taille millimétrique, réalisé par coextrusion, est une capsule à coeur liquide possédant une membrane d'hydrogel conducteur. La synthèse de ce bioréacteur a nécessité la formulation d'un hydrogel composite alginate/nanotubes de carbone en deux étapes. Une première étape rapide crée la matrice d'hydrogel par diffusion d'ions divalents dans un mélange Alginate/nanotubes de carbone. Une seconde étape, plus lente, permet la dialyse du tensioactif stabilisant les nanotubes et la création d'un réseau conducteur au sein de l'hydrogel pour des pourcentages massiques de charges supérieurs à 0,5 %. Ce matériau composite présente alors une conductivité macroscopique d'environ 0,1 S/m. Une étude du matériau par voie électrochimique permet entre autres de suivre cinétiquement la connexion des nanotubes de carbone. Des bactéries peuvent adhérer à la surface de cet hydrogel composite. Nous démontrons qu'il est alors possible de mesurer l'électroactivité d'un biofilm bactérien développé sur la paroi interne d'une capsule conductrice. Ce nouveau compartiment biocompatible ouvre la voie vers le développement d'un outil de criblage pour la sélection de bactéries électroactives mais offre également des perspectives innovantes pour la fabrication de piles bactériennes. / This work focuses on the creation of a new biocompatible reactor allowing the encapsulaion and the study of electroactive bacteria. Made by co-extrusion, this millimeter bioreactor is a liquid core capsule with a conducting hydrogel membrane. To create such an object, we formulate a composite hydrogel of alginate/carbon nanotubes in two steps. The first step is rapid and creates the hydrogel matrix by diffusion of divalent ions inside the alginate/carbon nanotubes mix. The second step is slower and permits the dialysis of the surfactant used to stabilize the nanotubes. During this last step, the carbone nanotube network percolates, creating a conducting network in the hydrogel for sufficient nanotube contents (above 0.5 %). This composite material has a macroscopic conductivity around 0.1 S/m. An electrochemical study of this material allows to follow the nanotube connection inside the hydrogel. Bacteria can adhere on this composite hydrogel. Then, we demonstrate that the electroactivity of a biofilm developped on the inner side of the conductive capsule shell can be measured. This new biocompatible and electron-conducting compartment opens the way towards the development of a screening tool for the selection of electroactive bacteria but also brings innovative perspectives in the field of microbial fuel cells fabrication.

Les films minces d'hydrogels thermosensibles à propriétés LCST/UCST (Lower/Upper Critical Solution Temperature) avec des températures de transition variables ont été mis au point pour des applications spécifiques. Les réseaux chimiques de polymères fixés de manière covalente sur des substrats solides plans ont été synthétisés par une approche polyvalente et facile à mettre en œuvre en utilisant la chimie click thiol-ène. Elle consiste à déposer des polymères préformés et réactifs en présence des réticulants dithiol sur des substrats modifiés thiol, la réaction de thiol-ène permettant la réticulation simultanée entre chaînes et le greffage en surface. La stratégie CLAG (Cross-Linking And Grafting) donne des films d'hydrogel chimiquement stables et reproductibles avec une large gamme d'épaisseur et avec les propriétés thermostimulables désirées. Les polymères hydrophiles fonctionnalisés par des groupes fonctionnels alcène peuvent être synthétisés en utilisant une copolymérisation radicalaire du monomère souhaité avec du méthacrylate d'allyle dans un solvant organique ou un co-solvant avec de l'eau. Une autre voie est la synthèse dans l'eau en deux étapes: le monomère désiré est copolymérisé avec l'acide acrylique puis le copolymère est modifié par l’allylamine. Trois familles de polymères ont été étudiées: poly(PEGMA), poly(acrylamide) et poly(zwitterion). La température de transition des films d'hydrogel est déterminée en mesurant l'épaisseur dans des solutions aqueuses par ellipsométrie. Les films d'hydrogel de poly(PEGMA) montrent des propriétés de LCST avec la température de transition augmentant avec le nombre d'unités de PEG. La LCST varie de 15°C à 60°C avec deux à cinq unités de PEG dans les chaînes pendantes. La LCST peut également être ajustée en utilisant des copolymères avec différents ratios. Les films d'hydrogel acrylamide ont à la fois des propriétés LCST et UCST. Les films d'hydrogel de poly(sulfobetaïne) montrent un comportement UCST très intéressant en plus d’être « anti-fouling », ce qui est très prometteur pour les applications en biologie. / Temperature-responsive surface-attached hydrogel thin films with various LCST/UCST (Lower/Upper Critical Solution Temperature) were designed for specific applications. The chemical polymer networks covalently attached on plane solid substrates were synthesized by a versatile and straightforward approach using thiol-ene click chemistry. It consists in coating ene-reactive polymers and dithiol crosslinkers on thiol-modified substrates, the thiol-ene click reaction allowing simultaneous cross-linking between chains and grafting on the surface. The CLAG (Cross-Linking And Grafting) strategy provides chemically stable and reproducible hydrogel films with a wide range of thickness and with the desired temperature-responsive properties. Ene-functionalized hydrophilic polymers can be synthesized using free radical copolymerization of the desired monomer with allyl methacrylate in organic solvent or co-solvent with water. Another way is the synthesis in water in two steps: the desired monomer is copolymerized with acrylic acid and then the copolymer is post-modified by amidification. Three polymer families were investigated: poly(PEGMA), poly(acrylamide) derivatives and poly(zwitterions). The transition temperature of the hydrogel films is determined by measuring the thickness in aqueous solutions at different temperatures with ellipsometry. Poly(PEGMA) hydrogel films show LCST properties with the transition temperature increasing with the number of PEG units. The LCST ranges from 15 °C to 60 °C with two to five PEG units in the pendant chains. The LCST can also be adjusted using mixed copolymers hydrogel. Poly(acrylamide) derivatives hydrogel films have both LCST and UCST properties. Poly(sulfobetaine) hydrogel films show very interesting UCST behavior in addition to be anti-fouling, which is very promising for biology applications.

Dans le but de réduire la morbidité et la durée d’hospitalisation, la médecine régénérative progresse de nos jours vers le développement de techniques chirurgicales moins invasives. Cette recherche en chirurgie mini-invasive a motivé le développement de matrices injectables pour l’ingénierie tissulaire osseuse. Ces matrices doivent aussi être capables de durcir une fois injectées in situ, acquérir la forme souhaitée ainsi que des propriétés mécaniques compatibles avec le tissu hôte qu’elles doivent réparer. De nombreux hydrogels sont déjà employés pour cette application mais aucun ne remplit complètement les propriétés requises. L’objectif de cette thèse est de développer de nouveaux substituts de greffe osseuse : des hydrogels à base de biopolymères associés à des cellules osseuses pour obtenir des greffons mi-synthétiques, mi-biologiques. Des nanoparticules de phosphates de calcium sont ajoutées pour améliorer les propriétés biologiques et mécaniques des hydrogels. L’hydroxyapatite, le phosphate de calcium choisi, est attrayante à cause de ses similitudes chimiques et structurales au constituent minéral de l’os humain. Le but de ce travail est de synthétiser des nanofils d’hydroxyapatite par la méthode template et des nanopoudres d’hydroxyapatite de taille contrôlée par sonoélectrochimie pulsée déphasée. Ensuite pour améliorer les propriétés intrinsèques des structures 3D, ces nanoparticules de phosphates de calcium seront insérées dans des matrices d’hydrogel synthétisées par le laboratoire d’ingénierie ostéo-articulaire et dentaire (LIOAD) de Nantes. Des mesures de coefficient de diffusion seront suivies par des tests de cytotoxicité et de biocompatibilité de ces matériaux. Des études en sous-cutané et après implantation en milieu osseux suivront. / In order to reduce morbidity and hospital stay, regenerative medicine is nowadays moving towards the development of less invasive surgical techniques. This search for a minimally invasive surgery has motivated the development of injectable matrices for bone tissue engineering. These matrices must also be able to harden in situ once injected, acquire the desired shape and mechanical properties compatible with the host tissue it intends to repair. Many hydrogels are already used for this application but none fully meets the required properties. The objective of this thesis is to develop new bone graft substitutes: hydrogels based on biopolymers associated with bone cells to achieve half synthetic and half biological grafts. Nanoparticles of calcium phosphates are added to improve the biological and mechanical properties of hydrogels. Hydroxyapatite, calcium phosphate chosen, has attracted much attention because of its chemical and structural similarity to the mineral constituent of human bone. The aim of this work is to synthesize firstly hydroxyapatite nanowires by the template method and secondly size controlled hydroxyapatite nanopowders by out-of-phase pulsed sonoelectrochemistry. Thirdly to improve the intrinsic properties of these three-dimensional structures, those nanoparticles of calcium phosphates will be added in the matrices of hydrogel synthesized by the LIOAD. Measurements of diffusion coefficient will be followed by testing cytotoxicity and biocompatibility of those materials. A subcutaneous study and bone model study will follow.