Stimuli-sensitive hydrogels are polymeric materials, which are able to reversibly swell in water in response to evironmental changes. Relevant stimuli include variations of pH, temperature, concentration of specific ions etc. Stacked layers composed of multiple thin hydrogels - also referred to as hydrogel-layer composites - combine the distinct sensing properties of different hydrogels. This approach enables the development of sophisticated micro uidic devices such as bisensitive valves or uid-sensitive de ectors. In order to numerically simulate the swelling of a polyelectrolyte hydrogel in response to an ion concentration change the multifield theory is adopted. The set of partial differential equations - including the description of the chemical, the electrical and the mechanical field - are solved using the Finite Element Method. Simulations are carried out on a twodimensional domain in order to capture interactions between the different fields. In the present work, the ion transport is governed by diffusive and migrative uxes. The distribution of ions in the gel and the solution bath result in an osmotic pressure difference, which is responsible for the mechanical deformation of the hydrogel-layer composite. The realized numerical investigation gives an insight into the evolution of the displacement field, the distribution of ions and the electric potential within the bulk material and the interface between gel and solution bath. The predicted behavior of the relevant field variables is in excellent agreement with results available in the literature.

We present recent results on a binary threshold sensor based on the binary zero-power sensor (BIZEPS) platform which is able to use the energy provided directly from the measured relative humidity of the ambient air to mechanically switch an electrical micro contact. This zero-power switch behavior is realized by using the humidity-sensitive volume swelling of a polymer layer as the detection element deflecting a mechanically deformable silicon boss structure, thus closing the electrical contacts of the switch. For the humidity-sensitive sensor switch considered here, a humidity-sensitive hydrogel blend of poly(vinyl alcohol) and poly(acryl acid) was used. The sensitive part affected by the measurand is completely separated from the electrical part, thus providing long-term stability. By using an inverse silicone stamping technique the polymer layer with a thickness of about 15 μm was patterned on test structures possessing a thin silicon flexure plate of 5 mm x 5 mm in size and 20 μm in thickness. Reproducible deformations of up to 15 … 24 μm has been measured. Investigations of the swelling kinetics showed for several discrete relative humidity values a saturation of the water load. The time to reach this saturation state is reduced from 5 hours down to approx. 20 min by increasing the relative humidity beyond the threshold value of 70% r.H. A significant influence of the temperature to the humidity load could not be observed.

Au cours des 30 dernières années, d'importants progrès ont été faits dans le domaine de l'oncologie. Les cancers pédiatriques ont été les grands bénéficiaires des progrès des thérapies anticancéreuses et aujourd'hui, le cancer de l'enfant peut être soigné, dans les pays développés, dans 75 à 80% des cas. Cependant, ces thérapies sont connues pour leurs effets gamétotoxiques, et seulement 33 % des garçons qui ont survécu à leur cancer durant l'enfance produisent du sperme de bonne qualité une fois arrivé à l'âge adulte. Actuellement, la seule mesure de préservation envisageable pour ces enfants est de procéder à un prélèvement et à une cryoconservation de tissu testiculaire. Aujourd'hui, il est donc important de mettre au point un procédé capable de produire des spermatozoïdes à partir de tissus testiculaire dans le but de restaurer leur fertilité. Pendant plusieurs décennies, les biologistes de la reproduction ont essayé de développer une technologie pour accomplir in vitro la spermatogenèse chez les mammifères. Malgré des investissements importants dans la recherche, aucune méthode n'a permis de reproduire in vitro l'ensemble de ce processus chez l'homme. Dans cette étude, la société de biotechnologie Kallistem a développée, en collaboration avec des partenaires académiques incluant le laboratoire Ingénierie des Matériaux Polymères (projet ARTIS financé par la Canceropôle Lyon Auvergne Rhône-Alpes) un système de culture tridimensionnel constitué d'un hydrogel de chitosane capable de réaliser in vitro l'ensemble de la spermatogenèse chez différents mammifères incluant l'homme. Le système de culture 3D est un hydrogel physique de chitosane sous forme de tube obtenu après neutralisation d'une solution aqueuse de chitosane, sans aucun agent réticulant. Avantageusement, le tissu testiculaire est confiné dans la lumière du tube ce qui permet de conserver l'architecture 3D in vivo des tissus. L'influence de plusieurs paramètres structuraux du chitosane et de paramètres liés au procédé d'élaboration sur la microstructure, les propriétés mécaniques et de diffusion des hydrogels a été évaluée, dans le but d'optimiser la capacité du système de culture à assurer la survie et la différentiation cellulaire / During the past 30 years, huge progress has been performed in the field of oncology. In particular, pediatric cancers have been the beneficiaries and can now achieve cure rates of 75-80% in developed countries. However, cancer therapies are known for their gametotoxic effects and only 33% of male children who have survived cancer during childhood produce sperm of normality quality when they are adults. Currently, the only feasible conservation protocol for these boys is to make a collection and cryopreservation of their testicular tissue. There is thus a need to provide a process enabling to produce spermatozoa starting from testicular tissue in order to restore fertility. For several decades, reproductive biologists have been trying to develop a technology to achieve spermatogenesis in vitro in mammals. Despite sustained investment in research, no method has now reproduced in vitro this entire process in humans. In this work, Kallistem (Biotech Company) has developed, in collaboration with academic laboratories including “Polymer Materials Engineering” laboratory (project ARTIS financed by the Cancéropôle Lyon Auvergne Rhône-Alpes) a 3D culture system made of chitosan hydrogel enabling to make a complete spermatogenesis in vitro in several mammals including human. The 3D culture system is a tube of chitosan physical hydrogel obtained from neutralization of aqueous chitosan solution, without any external cross-linking agent. Advantageously, the testicular tissue is confined in the lumen of tube which enables to reproduce in vivo 3-dimensional architecture. The impact of several material and processing parameters on microstructure, mechanical and diffusion properties of resulting hydrogels was evaluated, in order to optimize the culturing and maturation ability of 3D culture system

La bioinspiration consiste à analyser les systèmes naturels qui se sont adaptés parfaitement à leurs environnements pour développer des solutions ingénieuses. Ce projet de thèse aborde la thématique de la lubrification articulaire dans le but de développer un traitement contre l'ostéoarthrite (OA). Nous nous sommes inspirés des articulations synoviales, systèmes tribologiques très performants grâce aux interactions synergiques entre la structure unique du cartilage et les molécules lubrifiantes (ML) du fluide synovial (SF). Cependant, lors de l'OA des mécanismes inflammatoires et d'érosion mécanique aboutissent à la dégénérescence progressive du cartilage et la dégradation spécifique des ML du SF (aggrécane et lubricine). Des mimes des ML du SF ont été synthétisés reprenant leur structure particulière dite en écouvillon moléculaire (BB), structure responsable de la lubrification. Des tests tribologiques (SFA, tribomètre) ont montré que les BB garantissent à la fois une faible friction et une résistance à l'usure sur des surfaces dures de mica. Ceci est dû à la présence, sur nos EM, de groupements d'ancrage spécifiques assurant l’adsorption sur la surface de mica et à la formation d'enchevêtrements et d’interactions intermoléculaires avec l'acide hyaluronique de haut poids moléculaire, composant essentiel du SF. Des mimes de cartilage à base d'hydrogels de chitosane multicouches ont été également réalisés reprenant les principales propriétés architecturales du cartilage. En combinaison avec nos EM, ces hydrogels, matériaux poroélastiques fragiles, sont capables d’être lubrifiés avec une friction dans la gamme physiologique et une nette amélioration de leur usure / Bioinspiration consists in the design of materials inspired by biological systems which have developed ingenious solutions to suit their environment. This project deals with bioinspiration for joint lubrication and in particular for the development of treatments for patients suffering from osteoarthritis (OA). To do so, we took our inspiration from joints which are amongst the most efficient aqueous tribological systems. Their unique properties arise from the complex synergistic interactions between cartilage structure and the lubricant macromolecules of the synovial fluid (SF). However, during OA, inflammatory mechanisms as long as mechanical erosion result in the degeneration of cartilage and lubricant macromolecules (aggrecan and lubricin). Polymeric mimes of the SF have been synthesized based on the bottle-brush (BB) architecture of LUB and AGG which is responsible for the joint lubrication. Tribological tests (SFA, tribometer) showed that BB polymers provided mica surfaces with a low friction and a wear protection up to several megapascals, typically in the range of natural joints. This wear protection was essentially due to the incorporation of anchoring groups specific to mica tribopairs on the BB polymers and the intermolecular bridging and entanglements emerging between BB polymers and high molecular weight HA, another main SF component. Cartilage mimes composed of multilayered chitosan hydrogels were designed to mimic the basic features of cartilage. Along with our BB polymers, the hydrogels, which are poroelastic and fragile materials, provided a low friction and a great decrease of wear

L’objectif de ce travail de recherche est le développement d’un biomatériau original permettant la libération retardée de principes actifs afin de résoudre les problématiques de diffusion trop rapide ou incontrôlée souvent rencontrées avec les systèmes de délivrance classiques. Un assemblage « hybride » composé de liposomes incorporant le principe actif, eux-mêmes incorporés dans un hydrogel physique de chitosane a été mis au point dans le cadre de ce travail. Pour élaborer ce système, une suspension de liposomes préformés est ajoutée à une solution de chitosane avant sa gelification. Une caractérisation des différents composants ainsi qu’une optimisation de ce processus d’élaboration ont été effectuées au cours de cette thèse. Les propriétés de relargage ont été étudiées via l’incorporation d’une molécule hydrosoluble jouant le rôle de modèle de principe actif. La carboxyfluorescéine (CF), dosable par fluorescence, a permis de confirmer le concept de « relargage retardé » : la quantité de CF libérée au cours du temps est plus élevée lorsque cette dernière est directement incorporée dans l’hydrogel, par rapport au cas où elle est intégrée dans l’assemblage « hybride ». Sur la base de ces résultats, l’incorporation et le relargage de deux principes actifs, la rifampicine (RIF), un antibiotique à large spectre, et la lidocaïne, un anesthésique local anti-arythmique, ont également été étudiées. Ce travail a permis de confirmer les résultats obtenus pour la molécule modèle, à savoir un retard au relargage significatif pour les assemblages par rapport aux hydrogels sans liposome. Diverses caractérisations ont également été menées pour examiner les propriétés rhéologiques et la morphologie de ces assemblages. Ces résultats représentent une avancée intéressante pour la valorisation de tels assemblages « hybrides » dans le domaine biomédical, et mettent en évidence le rôle des liposomes en tant que « réservoirs » de principes actifs au sein même de ces assemblages. / This work deals with the development of an original biomaterial in view of its application as drug delayed-release device in biomedical area. To overcome classic issues that may be encountered with common drug delivery systems such as the “burst effect” or fast outside diffusion of drugs, a « hybrid » system composed of liposomes entrapped within a chitosan physical hydrogel was developed. Its elaboration process consists in the addition of a suspension of pre-formed phosphatidylcholine liposomes within a chitosan solution before gelation process. A characterization of different components of the system and an optimization of the elaboration process were achieved. The release properties were firstly investigated using a water-soluble fluorescent model molecule, carboxyfluorescein (CF). The concept of delayed-release was confirmed. Indeed, the release of CF, assayed by fluorescence spectroscopy, was found to be higher in the “drug-in-hydrogel” systems in comparison with the “drug-in-liposomes-in-hydrogels” ones. Based on these results, the release of two drugs, rifampicin (RIF), a broad spectrum antibiotic, and lidocaine (LID), a local anaesthetic and anti-arrhythmic drug, were also studied. This work corroborated the data obtained for the model molecule, that is to say a significant delayed release for « hybrid » systems in comparison to hydrogels without liposome. Various characterizations were carried out to examine rheological properties and morphologies of assemblies. These first results showed that such systems could be a step forward in drug delivery, and highlighted the use of liposomes as drug « reservoirs » within assemblies.

Space-resolved stimulation of active hydrogel layers can be achieved for example by using a micro-heater array. In the current work, we present the interaction of (i) such a rigid array of heating elements that can be selectively activated and (ii) an active thermo-responsive hydrogel layer that responds to the local stimulus change. Due to the respective local actuation, (iii) the surface form of a passive top-layer can be manipulated. We present continuum-based simulative predictions based on the Temperature Expansion Model and compare them to experimental outcomes for the system.

Bone transplantation is regarded as the preferred therapy to treat a variety of bone defects. Autologous bone tissue is often lacking at the source, and the mesenchymal stem cells (MSCs) responsible for bone repair mechanisms are extracted by invasive procedures. This study explores the potential of autologous mesenchymal stem cells derived from the hair follicle outer root sheath (MSCORS). We demonstrated that MSCORS have a remarkable capacity to differentiate in vitro towards the osteogenic lineage. Indeed, when combined with a novel gelatin-based hydrogel called Osteogel, they provided additional osteoinductive cues in vitro that may pave the way for future application in bone regeneration. MSCORS were also compared to MSCs from adipose tissue (ADMSC) and bone marrow (BMMSC) in a 3D Osteogel model. We analyzed gel plasticity, cell phenotype, cell viability, and differentiation capacity towards the osteogenic lineage by measuring alkaline phosphatase (ALP) activity, calcium deposition, and specific gene expression. The novel injectable hydrogel filled an irregularly shaped lesion in a porcine wound model displaying high plasticity. MSCORS in Osteogel showed a higher osteo-commitment in terms of calcium deposition and expression dynamics of OCN, BMP2, and PPARG when compared to ADMSC and BMMSC, whilst displaying comparable cell viability and ALP activity. In conclusion, autologous MSCORS combined with our novel gelatin-based hydrogel displayed a high capacity for differentiation towards the osteogenic lineage and are acquired by non-invasive procedures, therefore qualifying as a suitable and expandable novel approach in the field of bone regeneration therapy

Impaired wound healing and the resulting chronic wounds may cause significant morbidity and mortality. In these pathogenic wound environments, the ratio of inflammatory and anti-inflammatory cytokines is highly biased to the pro-inflammatory side. While the inflammatory process is an essential step in healthy wound healing, chronic wounds remain in a constant self-sustaining state of inflammation. Thus, decreased cell proliferation, reduced matrix deposition and delayed wound closure are the results. Although various cytokine-based therapies have shown promising results on skin regeneration in preliminary studies, their overall clinical use has been considerably limited by the short half-life time of the signaling molecules due to rapid dilution and degradation in the protease-rich chronic wound environment. In this work, we explored the ability of starPoly(ethylene glycol)-GAG hydrogels to modulate the hallmarks of chronic wound development, such as the prolonged inflammation, increased cell influx and delayed proliferative phase. Therefore, different strategies were developed to shape the cytokine levels in the wound towards a more pro-regenerative direction, finally promoting the natural repair process in chronic skin wounds. By biomimetically utilizing the interactions between cytokines and the tissue ECM in a GAG-based biohybrid hydrogel, we could engineer the concentrations of various signaling factors involved in the regulation of the repair process. More in detail, we utilized customized functionalized starPEG-GAG hydrogels to (1) reduce the extensive levels of inflammatory chemokines by scavenging them via GAG component of the hydrogel and thus diminish immune cell influx in a mouse wound model; (2) locally deliver the immunomodulatory IL-4 and IL-10 to shift the signaling balance into the pro-regenerative direction and thus resolve inflammation and (3) administer pre-conjugated TGF-β to enhance myofibroblast differentiation and extracellular matrix deposition. We believe that the presented hydrogel platform may become a promising tool in the management of cytokines in regenerative applications, which can be translated towards the clinical use for the treatment of chronic wounds and other diseases characterized by uncontrolled inflammation.:1 introduction 1.1 Motivation 1.2 Current state of biomaterial-based concepts in dermal wound healing 1.3 Objective 2 fundamentals 2.1 The physiological process of wound healing 2.1.1 The role of macrophages in wound healing 2.1.2 The role of fibroblasts in wound healing 2.1.3 The role of cytokines and their interaction with the ECM 2.2 The pathophysiology of chronic wounds 2.3 Strategies for treatment of chronic wounds 2.4 Biomaterials in medicine 2.4.1 Polymers in medicine 2.4.2 Mechanical properties 2.4.3 Cellular adhesion 2.4.4 Interaction with cytokines 2.4.5 Scaffold degradability 2.4.6 StarPEG-GAG hydrogels as potential material in wound healing 3 materials & methods 3.1 Preparation of hydrogels 3.1.1 Functionalization of glass surfaces 3.1.2 Hydrogel formation with EDC - NHS chemistry 3.1.3 Hydrogel formation with thiol - maleimide chemistry 3.1.4 Rheometric measurement of hydrogel discs 3.1.5 Characterization of cytokine uptake and release 3.2 Culture of human & murine cells 3.2.1 Isolation and differentiation of murine dermal fibroblasts 3.2.2 Isolation & differentiation of murine macrophages 3.2.3 Culture of human & murine cell lines 3.3 In vitro methods 3.3.1 Enzyme-linked immunosorbent assay (ELISA) 3.3.2 Bead-based multiplex immunoassay 3.3.3 Live/Dead Staining 3.3.4 Crystal violet staining 3.3.5 Cell proliferation assay 3.3.6 RNA extraction & analysis 3.3.7 cDNA synthesis 3.3.8 Quantitative real time rt-PCR 3.4 Statistical analysis 3.5 Software use 4 scavenging inflammatory chemokines to control immune cell influx in the wound 4.1 Results 4.1.1 Engineering heparin-based hydrogels to scavenge chemokines 4.1.2 Heparin-based hydrogels reduce migration of immune cells 4.1.3 Heparin-based hydrogels decrease wound immune cell influx and inflammatory signaling 4.2 Discussion 5 promotion of regenerative macrophage polarizationin inflammatory environments 5.1 Results 5.1.1 Reversible complexation of IL-4 & IL-10 to starPEG-heparin gels 5.1.2 Stabilizing effects of starPEG-heparin gels on IL-4 5.1.3 IL-4 & IL-10-laden starPEG-heparin hydrogels modulate macrophage polarization 5.1.4 IL-4-laden starPEG-heparin induce collagen deposition in dermal fibroblasts 5.2 Discussion 6 modulation of human dermal fibroblast proliferation and differentiation 6.1 Results 6.1.1 Reversible complexation of TGF-b to starPEG heparin gels 6.1.2 Cell attachment, spreading and proliferation 6.1.3 Matrix deposition by fibroblasts grown on starPEG-heparin hydrogels 6.1.4 Degradation of starPEG-heparin hydrogels 6.1.5 TGF-b-laden starPEG-heparin that efficiently induces myofibroblast differentiation 6.2 Discussion 7 general discussion 7.1 Summary and conclusion 7.2 Future perspective Appendix 8 supplementary materials & methods 9 declaration of authorship 10 publications and conference contributions bibliography list of figures list of tables nomenclature selbstständigkeitserklärung

Diese Arbeit liefert Informationen über die neuartige Synthese von physikalischen durch Glycin vernetzten Cellulosehydrogelen. Ihre Herstellung, Morphologie, Wasseraufnahmevermögen, mechanische und thermische Eigenschaften, Wiederverwendbarkeit und Stabilität werden detailliert beschrieben. Die Arbeit präsentiert eine umfassende Studie über die Herstellung, Charakterisierung, Morphologie und thermischen Eigenschaften von Hydrogelen und validiert die Verwendung von Cellulose-Glycin-Hydrogelen für Anwendungen mit abgeschiedenen Goldnanopartikeln. / This thesis provides information about the novel synthesis of cellulose hydrogels physically crosslinked by glycine; their fabrication, morphology, water absorption capacity, mechanical properties, thermal properties, reusability, stability and gold nanoparticle deposition. The work validates also the use of cellulose–glycine hydrogels for gold nanoparticle deposition applications and presents a comprehensive study of gold nanoparticle deposited hydrogels about their fabrication, characterization, morphology and thermal properties.

Enzymes and subcritical water can be used for the extraction of hemicelluloses from cereal by-products, making the processes eco-friendly. The polysaccharides extracted from cereal by-products can be used as matrices for development of materials for various applications. This includes bio-based materials such as films and hydrogels, which offer alternatives to existing materials produced from petrochemicals. The polymeric structure of cereal hemicelluloses contains functional groups which enable the modification of their structure by cross-linking, resulting in the formation of hydrogels. This project aims to use subcritical water extraction (SWE) to extract arabinoxylans (AXs) from corn and rye bran meanwhile the enzymatic treatment is done for purifying the samples during both pre- and post-treatment. AXs were further crosslinked by enzyme (laccase) for hydrogel preparation. During the whole project, the characterization included moisture and yield determination, starch and protein content which were tested using a spectrophotometer, monosaccharide content was analyzed by high performance anion exchange chromatography followed by pulsed amperometric detection (HPAEC-PAD) and phenolic acid content was quantified by high performance liquid chromatography (HPLC). The pretreatment for destarching and SWE process was successful. The result showed that arabinoxylans form corn bran were having higher content of arabino substituents, arabino toxylans ratio and ferulic acid content than rye samples. The enzymatic crosslinking could form strong gels in the condition that the AXs had high ferulic acid content. In terms of forming strong hydrogels or to improving the properties of AXs gel, the pre- and post-treatment should be optimized to increase the purity of the extracted feruloylated AX content. / Enzymer och subkritiskt vatten kan användas för extraktion av hemicellulosa från spannmålsbiprodukter, vilket gör extraktionen miljövänlig. Polysackariderna extraherade från spannmålsprodukter kan användas som matriser för utveckling av material för diverse applikationer. Detta inkluderar biobaserade material som filmer och hydrogeler, där petrokemikalier kan ersättas som råvara. Den polymera strukturen hos spannmålshemicelluloser innehåller funktionella grupper som möjliggör formation av tvärbindningar vilket resulterar i bildandet av hydrogeler. Syftet med detta projekt är extraktion av arbinoxylaner (AXs) från majs och rågkli genom att använda subkritiskt vatten-extraktion (SWE) där rening under för- och efterbehandling utförs enzymatiskt. AX modifierades därefter enzymatiskt (laccas) med tvärbindningar för hydrogelframställning. Under hela projektet karakteriserades hydrogelen utifrån fuktinnehåll, bestämmelse av utbyte, stärkelse och proteininnehåll som testades med en spektrofotometer, monosackaridhalten analyserades med högpresterande anjonsutbyteskromatografi följt avpuls-amperometrisk detektion (HPAEC-PAD), samt kvantifierades fenolsyrahalten med högupplöst vätskekromatografi (HPLC). Resultatet visade att arabinoxylaner från majskli hade högre innehåll av arabinosubstituenter, där förhållandet mellan arabino och xylans, samt arabino och ferulsyra innehållet var högre än för rågproverna. Den enzymatiska tvärbindningen kunde bilda starka geler i det tillståndet där AX hade en hög ferulsyrahalt. När det gäller att bilda starka hydrogeler eller att förbättra egenskaperna hos AXs-gel, bör för-och efterbehandlingen optimeras för att öka renheten fördet extraherade feruloylerade AX-innehållet.