Le phénomène de biofouling affecte toute surface immergée dans un milieu aqueux, le recouvrant par un biofilm que ce soit dans le milieu médical ou marin. Afin de lutter contre ce phénomène, lors de ce travail, des matériaux biosourcés à base d’alginate ont été élaborés. Pour des applications dans le milieu médical, des films d’hydrogel de surface lisse ou poreuse et des films déposés sur acier par électrophorèse ont été élaborés. La présence de cuivre et zinc sous leur forme ionique Cu2+ et Zn2+ a été démontrée. Tous les films à base de cuivre et de zinc ont montré des propriétés antibactériennes contre des souches de bactéries pathogènes. Des volumes d’hydrogel d’alginate à base de calcium, cuivre et zinc ont été aussi élaborés pour des applications dans le monde marin. La stabilité des différents matériaux a été étudiée dans différents milieux et à différentes températures. La propriété antimicrobienne de ces hydrogels a été démontrée sur deux souches de microalgues ainsi que sur quatre souches de bactéries marines sans toxicité. Finalement, le retardement de la formation de biofilms sur la surface d’acier inoxydable a été étudié par la méthode d’OCP en présence de matériaux à base de zinc. / Biofouling is a phenomenon that affects every surface that is immersed in an aquatic medium covering it by a biofilm either in the medical or marine field. In order to prevent this phenomenon, in this work, biosourced alginate materials were elaborated. For applications in the medical field, hydrogel films of smooth or porous surface and films coating stainless steel by electrophoresis were elaborated. The presence of copper and zinc in their ionic form Cu2+ and Zn2+ was demonstrated.All the copper and zinc based films showed antibacterial properties on pathogenic bacterial strains.Alginate hydrogels in bulk based on calcium, copper and zinc were also elaborated for applications in the marine field. Stability of the different materials was studied in different mediums and at different temperatures. The antimicrobial property of these hydrogels based on copper and zinc was demonstrated on two microalgae stains as well as on four marine bacteria strains with no sign of toxicity. Finally, the delay in the formation of biofilms on stainless steel surfaces was studied by the OCP method in the presence of zinc based materials.

Polymeric excipients are generally the least well-characterized components of pharmaceutical formulations. The aim of this dissertation work is to facilitate the quality-by-design (QbD) approach to pharmaceutical formulation and manufacturing by evaluating the inter-grade and inter-batch variability of pharmaceutical-grade polymeric excipients. Sodium alginate, a widely used polymeric excipient, was selected for evaluation using appropriate analytical methods and test conditions, especially rheological methods. The materials used were six different grades of sodium alginate and an additional ten batches of one of the grades. <br>To compare the six grades, steady shear measurements were conducted on solutions at 1, 2, and 3% w/w, consistent with their use as thickening or binding agents. Small amplitude oscillation (SAO) measurements were conducted on sodium alginate solutions at higher concentrations (4-13% w/w) corresponding to their use in controlled release matrices. In order to compare the ten batches of one grade, steady shear and SAO measurements were performed on their solutions at 2% w/w and 8% w/w, respectively. Results show that rheological properties of sodium alginate solutions are influenced by both molecular weight and chemical composition of sodium alginate. ¡§One-point¡¨ apparent viscosity data obtained at one low concentration and one shear rate is not representative of the complex rheological behavior of various grades of sodium alginate solutions at higher concentrations or other shear rates. The potential interchangeability of these different grades used as thickening or binding agents could be established by comparing the apparent viscosities of their solutions as a function of both alginate concentration and shear conditions. For sodium alginate used in controlled release formulations, both steady shear (at one low concentration, e.g., 2% w/w) and SAO measurements (at one high concentration indicative of polymer gel state, e.g., 8% w/w) are recommended to be performed on sodium alginate solutions to ensure interchangeability. Furthermore, among batches of the same grade, significant differences in rheological properties were observed, especially at the high solution concentration (i.e., 8% w/w). In summary, inter-grade and inter-batch variability of sodium alginate can be determined using steady shear and SAO methods. <br>The influence of inter-grade and inter-batch variability of sodium alginate on the functionality of sodium alginate used in matrix tablets was investigated with a focus on compression properties, swelling, erosion behavior of alginate matrix tablets, and drug release from matrix tablets. The compression behavior of four grades and three batches of sodium alginate were studied by compaction energetics, out-of-die Gurnham, and out-of-die Heckel analysis. It was found that sodium alginates deform less plastically than microcrystalline cellulose (MCC PH102) but similar to lactose anhydrous. Sodium alginates also demonstrate more elastic deformations during compression than both MCC PH102 and lactose anhydrous. Compacts prepared from multiple batches of the same grade varied in porosity. The same tensile strength of compacts can be achieved by compressing the multiple batches to the same porosity. <br>Sodium alginate tablets undergo both swelling and erosion in water. Grades with substantially higher apparent viscosities at low solution concentration exhibit a higher percentage of water uptake and a low percentage of erosion. Those batches not significantly different in their apparent viscosities at low solution concentration but significantly different in viscoelasticity at high solution concentrations do demonstrate significant differences in their swelling and erosion behavior. Acetaminophen release from sodium alginate matrix tablets prepared from the four grades and three batches can be well described by a zero-order equation. Significant differences in release profile were observed among various grades and batches. <br>In conclusion, the inter-grade and inter-batch variability of sodium alginate has a significant influence on the swelling, erosion, and drug release behavior of sodium alginate matrix tablets. Apparent viscosities of sodium alginate solution at low concentration alone are not sufficient to predict the functionality of sodium alginate used in matrix tablets. Viscoelastic properties of sodium alginate solutions at high concentrations indicative of polymer gel state are appropriate to be characterized. <br>Further study was conducted to determine whether sodium alginate solutions¡&brkbar; rheological parameters are relevant to sodium alginate¡&brkbar;s use in the formulation of calcium alginate gels. Among the grades with similar guluronic acid percentage (%G), there is a significant correlation between gel fracture force and apparent viscosity. However, the results for the partial correlation analysis for all six grades of sodium alginate show that gel fracture force is significantly correlated with %G, but not with the rheological properties of the sodium alginate solutions. Studies of the ten batches of one grade of sodium alginate show that apparent viscosities of their solutions do not correlate with gel fracture force while tan <em>f</em>Ô values are significantly, but minimally, correlated to gel fracture force. Inter-batch differences in the rheological behavior for one specific grade of sodium alginate are insufficient to predict the corresponding calcium alginate gel's mechanical properties. <br>In summary, rheological methods, including steady shear and small amplitude oscillation, are able to identify the inter-grade and inter-batch variability of sodium alginate. Inter-grade and inter-batch variability of sodium alginate could lead to substantial differences in the functionality of sodium alginate in matrix tablets and in calcium alginate gels. Rheological properties of sodium alginate in solution are suggestive of its functionality as thickeners, or as controlled release agent. However, rheological properties of sodium alginate in solution do not seem to be sufficient to predict the mechanical properties of the corresponding calcium alginate gels. / Mylan School of Pharmacy and the Graduate School of Pharmaceutical Sciences / Pharmaceutics / PhD / Dissertation

Avec une mortalité après pancréatectomie de l'ordre de 5 % et une morbidité aux alentours de 50 %, la chirurgie pancréatique est l'une des plus délicates des interventions digestives. L'une des complications les plus graves est l'apparition de fistules pancréatiques (FP), c'est-à-dire un défaut d'imperméabilisation au niveau des sutures, impliquant une fuite enzymatique dans le milieu péritonéal qui peut engager le pronostic vital du patient. A ce jour, aucun dispositif médical n'est indiqué dans la prévention de ces FPs. Ainsi, ce projet a pour ambition de concevoir et de valider un biomatériau constitué d'une matrice absorbante qui assurera la double fonction d'éponge et de réservoir d'agent antibactérien, sur laquelle un greffage chimique devrait conférer des propriétés bioadhésives thermorégulées. La première partie de ce travail est consacrée à l'optimisation de la matrice absorbante, à base d'alginate et de chitosane, déjà développée lors d'une précédente thèse. Trois types de procédés de séchages ont été comparés : le séchage par évaporation, la lyophilisation et le séchage en milieu CO2 supercritique. Ces différents procédés conduisent à des matériaux de structures internes et de porosités différentes. L'impact de ces différences de structure a été évalué en termes de capacité de gonflement dans différents milieux, dont un milieu pancréatique simulé, mais aussi en termes de résistance enzymatique et de libération de principe actif. En tenant compte des résultats obtenus, le séchage par évaporation a été identifié comme le plus approprié pour la suite de l'étude. Dans une deuxième partie, du poly(N-isopropylacrylamide) (PNIPAM) a été synthétisé par polymérisation contrôlée (RAFT) afin d'être greffé sur la matrice absorbante. Le PNIPAM est un polymère thermosensible dont les propriétés bioadhésives sont directement dépendantes de la température. Ce polymère est généralement bioadhésif au-dessus de sa " lower critical solution température " (LCST), située aux alentours de 32 °C. Dans cette étude la masse molaire et la densité de greffage du PNIPAM sont les deux principaux paramètres étudiés pour son greffage sur les matrices. Enfin, les propriétés de surface des matrices greffées ont été caractérisées. Les matériaux ont montré, in vitro, des propriétés bioadhésives thermosensibles, avec une bioadhésion cellulaire observée principalement au-delà de la LCST. Les essais ex vivo ont cependant montré une bioadhésion sur organe plus importante en dessous de celle-ci. Cette étude a permis de mettre au point des biomatériaux absorbants aux propriétés de surface thermorégulées. Une compréhension plus fine des relations propriétés de surface/propriétés d'usage permettrait d'optimiser les propriétés de bioadhésion thermorégulée. / Pancreatic surgery, which leads to 5 % of mortality and around 50 % of morbidity, is one of the most critical digestive operations. The most serious complication is the appearance of pancreatic fistulas (PFs), i.e. enzymatic leaks from the surgical sutures to the peritoneal environment that can lead to the life threatening of the patient. To date, no medical device is indicated for the prevention of these FPs. The aim of this project is to design and validate a biomaterial constituted of a matrix that will ensure the dual function of absorbent and antibacterial agent reservoir, on which a chemical grafting should confer thermoregulated bioadhesive properties. The first part of this work is devoted to the optimisation of the absorbent matrix, based on alginate and chitosan, already developed during a previous thesis. Three types of drying processes were compared: drying by evaporation, lyophilisation and drying in supercritical CO2 medium. These different processes led to materials with different internal structures and porosities. The impact of these structures was evaluated in terms of swelling capacity in various media, including a simulated pancreatic environment, but also in terms of enzymatic resistance and release of an active molecule. Taking into account the obtained results, drying by evaporation was identified as the most appropriate process. In a second part, poly (N-isopropylacrylamide) (PNIPAM) was synthesised by controlled polymerisation (RAFT) in order to be grafted onto the absorbent matrix surfaces. PNIPAM is a thermosensitive polymer with bioadhesive properties which depend on the temperature. This polymer is usually bioadhesive above its lower critical solution temperature (LCST), around 32 ° C. In this study, the molar mass and the grafting density of PNIPAM are the two main parameters studied for the surface modifications. Finally, the surface properties of the grafted matrices were characterised. In vitro, the materials showed thermosensitive bioadhesive properties, with a cellular bioadhesion mainly observed above the LCST. However, ex vivo tests exhibited higher bioadhesion on porcine organs at lower temperatures. This study led to the development of absorbent biomaterials with thermoregulated surface properties. Further understanding of the relationship between surface properties and in vivo bioadhesion would allow the optimisation of the thermoregulated surface properties.

L'implantation d'îlots de Langerhans microencapsulés est une thérapie prometteuse pour le diabète de type 1. Le concept est de rétablir la fonction de sécrétion d'insuline tout en évitant le rejet de greffe. Les premiers essais cliniques ont reporté des résultats encourageants mais encore peu reproductibles. En effet, les techniques actuelles de production de microcapsules sont manuelles et au sein d'un même lot les capsules ne sont pas homogènes. L'utilisation de la microfluidique offre la possibilité de remédier à ce problème. Ce projet présente les différentes étapes d'optimisation d'un système microfluidique complexe qui automatise le procédé d'encapsulation monocouche de cellules dans des capsules polymériques d'alginate. Ce système comporte trois fonctions principales en série : la formation de gouttes monodisperses d'alginate en flux d'huile par un module MFFD (Micro Flow Focusing Device), le transfert de ces gouttes de la phase huileuse vers une phase aqueuse gélifiante de calcium et enfin un second transfert vers un flux à concentration physiologique. Des capsules monodisperses et sphériques ont été obtenues en sortie de ce système et des premiers tests d'encapsulation de cellules ont été réalisés. Les capsules produites par le système automatisé ont conduit à une première implantation chez le rongeur. Ce système est une première étape clé vers un dispositif instrumenté qui permettrait aux cliniciens d'encapsuler des îlots rapidement et de façon reproductible directement après leur isolement, puis de les implanter chez les patients diabétiques. Mots clés : encapsulation, îlots de Langerhans, alginate, gélification, microfluidique, automatisation, MFFD, transfert de phase. / Epileptic seizures arise from pathological synchronization of neuronal ensemble.Seizures originating from primary motor cortex are often pharmacoresistant, and many times unsuitable for respective surgery because of location of epileptic focus in eloquent area. Basal ganglia play important role in seizure propagation. Micro electrode recordings performed during previous studies indicated that input structures of basal ganglia such as GPe, Putamen and Subthalamic nucleus (STN) are strongly modified during seizures. For example the mean firing rate of neurons of the STN and Putamen increased and the percentage of oscillatory neurons synchronized with the ictal EEG was higher during seizures as compared to interictal periods. Pilot studies in humans have shown the possible beneficial effect of chronic DBS applied to STN in treatment of pharmacoresistant motor seizures. Our study was aimed at studying the therapeutic effect of electrical stimulation of input structures of basal ganglia . We first developed a stable, predictable primate model of focal motor epilepsy by intracortical injection of penicillin and we documented it's pharmacoresistence. We then stereotactically implanted DBS electrodes in the STN and Putamen. The stimulator was embedded at the back of the animals. Subthreshold electrical stimulations at 130 Hz were applied to STN. Stimulator was turned ON when penicillin was injected. Sham stimulation at 0 volt was used as a control situation, each monkey being its own control. The time course, number and duration of seizures occurring in each epochs of 1 h were compared during ON and sham stimulation periods. Each experimental session lasted uptoo 6 hours,We also studied preventive high frequency stimulation of STN and subthershold low frequency stimulation of Putamen with 5 Hz and 20 Hz in the same model .Finally we studied combined effects of high frequency STN and low frequency Putamen stimulation in one monkey Results: Data was analysed from 1572 seizures in 30 experiments in three monkeys for chronic STN stimulation , 454 seizures in 10 experiments in one moneky during preventive STN stimulation ,289 seizures from 14 experiments in two monkeys during LFS putamen stimulation and 477 seizures from 10 sessions during combined STN and Putamen stimulation in one monkey The best results were observed during chronic STN stimulation The occurrence of first seizure was significantly delayed as compared to sham situation. Total time spent in focal seizures was significantly reduced by ≥69% on an average (p ≤0.05) after STN stimulation, due to a significant decrease in the number of seizures especially so during the first 3 hours after stimulation. The duration of individual seizures reduced moderately. Bipolar and monopolar stimulation modes were equally effective Preventive HFS STN (in one specimen) was not found to be superior to acute stimulation. LFS Putamen alone was effective but mainly in first two hours of stimulation .In a combined HFS STN and LFS Putamen stimulation the effect of stimulation in terms of seizure control was modest and poor compared to HFS STN alone or LFS Putamen alone. This study provides original data in primates showing the potential therapeutic effect of chronic HFS-STN DBS to treat focal motor seizures . A discussion explaining these

Les composés organiques volatils (COV) contribuent fortement à la pollution atmosphérique. Plusieurs techniques sont possibles pour leur élimination parmi lesquelles, l'oxydation catalytique est une alternative intéressante. Ces dernières années de nombreux efforts ont été entrepris pour la conception de catalyseurs à base d'oxyde de métaux de transition afin de remplacer les métaux nobles, généralement plus actifs pour cette réaction, mais chers. Le principal objectif de cette thèse est le développement de nouveaux catalyseurs à base d'oxyde métallique pour l'élimination du toluène, choisi comme modèle de COV, utilisant l'air comme oxydant. Les catalyseurs ont été préparés à partir de gels ionotropiques d'alginate. Ce biopolymère, un polysaccharide extrait des macro-algues brunes, est un copolymère à blocs fonctionnalisés sur chaque sucre par une fonction carboxylate. La coordination des cations conduit à la formation des gels. Après séchage, la matrice est sacrifiée par traitement thermique et cette voie de synthèse permet d'aboutir à des oxydes métalliques non supportés mais bien dispersés, ainsi qu'un contrôle de la structure, de la composition et de la taille des particules. Tous les matériaux obtenus à base de Fe, Co, Mn, Cu, sont caractérisés par DRX, TPR, MEB, MET, ATG, XPS, EDS, AE, adsorption-désorption d'azote. Parmi les oxydes (oxydes simples et mixtes) évalués comme catalyseurs dans la réaction d'oxydation totale du toluène en phase gaz, l'oxyde mixte cuivre-manganèse a été le plus prometteur. Sa performance est attribuée à la présence de la phase mixte de type spinelle Cu1.5Mn1.5O4 obtenus indépendamment de la structure de l'alginate. Ce catalyseur n'a pas montré de désactivation en fonction du temps (75 h) ni au cours de cycles successifs d'utilisation. Ses propriétés texturales et structurales sont conservées. Enfin, plusieurs modèles cinétiques (loi de puissance, modèle de Langmuir – Hinshelwood et le modèle de Mars-van Krevelen) ont été ajustés aux données expérimentales. L'analyse complète des données cinétiques a permis de conclure que la vitesse de réaction d'oxydation totale du toluène en phase gaz sur l'oxyde mixte cuivre manganèse, est mieux décrite par un modèle de type Mars-van Krevelen. / Volatile organic compounds (VOCs) contribute significantly to air pollution. Several techniques are available for their elimination including the interesting catalytic oxidation. In recent years many efforts have been made to design catalysts based on transition metal oxide to replace noble metals, usually more active for this reaction, but more expensive. The main objective of this thesis is the development of a new synthesis way to produce catalysts based on metal oxide for the removal of toluene, chosen as a model VOC, using air as oxidant. The catalysts were prepared using ionotropic alginate gels as precursors. This biopolymer, a polysaccharide extracted from brown macroalgae is a block copolymer functionalized on each sugar unit by a carboxylate function. The carboxylate- cations coordination leads to the formation of gels. After drying, the matrix is eliminated by thermal treatment and this synthesis route can lead to unsupported but well dispersed metal oxides with a good control of the structure, composition and particle size. All materials obtained based on Fe, Co, Mn, Cu, were characterized by XRD, TPR, SEM, TEM, TGA, XPS, EDS, EA, and adsorption-desorption of nitrogen. Among the oxides (single and mixed oxides) evaluated as catalysts in the reaction of toluene oxidation in gas phase, the copper manganese oxide was the most promising catalyst. Its performance is attributed to the presence of the spinel mixed phase Cu1.5Mn1.5O4, obtained independently of the alginate structure. This catalyst showed no deactivation over time (75 h) or after successive uses. Its textural and structural properties were preserved. Finally, several kinetic models (power law model, Langmuir - Hinshelwood model and Mars-van Krevelen model) were fitted on experimental data. The complete analysis of the kinetic data allowed to conclude that the rate of toluene total oxidation reaction in gas phase on copper manganese mixed oxide, is best described by a Mars-van Krevelen model.

Ce travail porte sur le développement de systèmes d’encapsulation à base de polysaccharides et de molécules antimicrobiennes de nature protéique comme le lysozyme du blanc d’œuf et la nisine produite par la bactérie Lactococcus lactis. La coacervation complexe de l’alginate ou la pectine (deux polysaccharides anioniques) avec le lysozyme ou la nisine, chargés positivement sur une large gamme de pH, serait une solution pour protéger ces molécules et assurer une libération contrôlée lors de la conservation d’un aliment. Les polysaccharides utilisés ont été choisis en fonction de leur sensibilité aux enzymes produites par les bactéries cibles. L’ensemble des travaux menés à différentes échelles a mis en évidence (i) le rôle de certains facteurs physico-chimiques (ratio, pH, force ionique,…) sur les interactions mises en jeu entre le lysozyme ou la nisine et l’alginate ou la pectine, (ii) l’influence de ces facteurs sur les propriétés des complexes formés et (iii) le rôle des polysaccharides sélectionnés dans la stabilisation de la structure du lysozyme ou de la nisine lors du séchage par atomisation. Enfin, la structure et l’activité antimicrobienne des films obtenus par voie solvant (casting) et des microcapsules obtenues par atomisation sont étudiées en relation avec les propriétés des complexes formés. Ce travail a permis une meilleure compréhension des mécanismes impliqués dans la formation des complexes peptides/polysaccharides ou protéines/polysaccharides, leur résistance au séchage par atomisation ainsi que leur capacité à protéger et à libérer des molécules actives / This work deals with the development of encapsulation systems based on polysaccharides and antimicrobial molecules of protein nature such as hen egg-white lysozyme and nisin produced by Lactococcus lactis. Complex coacervation of alginate or pectin (two anionic polysaccharides) with lysozyme or nisin, positively charged over a wide range of pH, would be a solution to protect these molecules and ensure their controlled release during food preservation. The used polysaccharides were chosen according to their sensitivity to the enzymes produced by the targeted bacteria. The whole of this work performed at various levels showed (i) the impact of some physicochemical factors (ratio, pH, ionic strength,…) on the interactions between lysozyme or nisin and alginate or pectin, (ii) the influence of these factors on the properties of the formed complexes, and (iii) the role of the selected polysaccharides in stabilizing the structure of lysozyme or nisin during spray-drying. Finally, the structure and the antimicrobial activity of films produced by casting and microcapsules obtained by spray-drying were studied in relation to the properties of the formed complexes. This work makes it possible to contribute to a better understanding of the various mechanisms implied in the formation of peptide/polysaccharide or protein/polysaccharide complexes, their resistance to spray-drying and their ability to protect and release active molecules

Dans ces travaux de recherche, la préparation de fibres d'alginate de calcium revêtues de chitosane par un procédé de filage par mouillage et la caractérisation de ces fibres dont leur activité antibactérienne sont présentées. Un métier à filer à l'échelle pilote a été conçu et développé au cours de ces travaux de thèse pour l'élaboration de fibres d'alginate de calcium. Ces dernières, préalablement fabriquées, sont immergées dans une solution d'acétate de chitosane. Trois méthodes de coagulation de l'enduit de chitosane ont été explorés dont deux consistent en l'immersion des fibres dans un bain neutralisant : une solution de dihydroxyde de calcium ou une solution d'hydroxyde de potassium. La dernière méthode consistait à neutraliser le chitosane par séchage sous air chaud soufflé. Une caractérisation structurelle, mécanique et d'absorption des fibres, ainsi qu'un dosage du chitosane revêtu ont été réalisés. De plus, une évaluation antibactérienne a été accomplie par une méthode de comptage des UFC (Unité Formant Colonie) après 6 h d'incubation à 37 °C. L'incorporation de chitosane aux fibres d'alginate de calcium apporte une activité antibactérienne contre Staphylococcus epidermidis, Escherichia coli et divers Staphylococcus aureus tels que MSSA (Methicillin Sensitive Staphylococcus aureus), CA-MRSA (Community Associated Methicillin Resistant Staphylococcus aureus) et HA-MRSA (Healthcare Associated Methicillin Resistant Staphylococcus aureus). Ces fibres revêtues sont alors des candidats de choix pour l'élaboration de tissus destinés à la cicatrisation des plaies. Développer des compresses avec les propriétés hémostatiques et cicatrisantes de l'alginate de calcium combinées aux propriétés antibactériennes du chitosane peut être envisagé pour lutter contre les infections et plus particulièrement les maladies nosocomiales / In this work, the preparation of chitosan-coated alginate fibers by a wet spin process and the characterization of these fibers, particularly their antibacterial activities are presented. A pilot scale spinning machine was developed during this thesis for the elaboration of calcium alginate fibers. These last, preformed produced were immersed in chitosan acetate solutions. Three coagulation methods of the chitosan coating were explored two of which consist to the immersion of the fibers in a neutralizing bath: a calcium hydroxide solution or a potassium hydroxide solution. The last method is to neutralize chitosan by drying under hot air blown. Structural, mechanical and absorption characterization of fibers and a dose of the coated chitosan have been made. Furthermore, the antibacterial evaluation was achieved by a CFU (Colony-Forming Units) counting method after 6 h of incubation at 37 °C. The incorporation of chitosan on calcium alginate fibers brings antibacterial activities against Staphylococcus epidermidis, Escherichia coli and various Staphylococcus aureus strains namely MSSA (Methicillin Sensitive Staphylococcus aureus), CA-MRSA (Community Associated Methicillin Resistant Staphylococcus aureus) and HA-MRSA (Healthcare Associated Methicillin Resistant Staphylococcus aureus) which make these chitosan-coated fibers potential candidates for wound dressing materials. Developing a wound dressing with the haemostatic and healing properties of alginate combined with antibacterial properties of chitosan can be envisioned for fighting against the infections and more particularly nosocomial infections

Biocatalysis and enzyme technology represent significant research topics of contemporary biotechnology. The immobilisation of these catalysts on or in static supports serves the purpose of transforming the catalyst into a particle that can be handled through effortless mechanical operations, while the entrapment within a membrane or capsule leads to the restraint of the enzyme to a distinct space. This confinement leads to a catalyst with a superior stability, and cell durability under reaction conditions. Epoxide hydrolase is a widely available co-factor independent enzyme, which is known to have remarkable chemio-, regio- and stereoselectivity for a wide range of substrates. Recently it was found that certain yeasts, including Rhodosporidium toruloides, contain this enzyme and are able to enantioselectively catalyse certain hydrolysis reactions. The objective of this project was four-sided: a) to immobilise Rhodospridium toruloides in an optimised immobilisation matrix (calcium alginate beads), for the kinetic resolution of 1.2- epoxyoctane in order to obtain an optically pure epoxide and its corresponding vicinal diol, b) to determine the effect of immobilisation on activity as well as stability of the enzyme and gain better understanding of the parameters that influence enzyme activity in a support, c) to determine the effect of formulation parameters on some of the bead characteristics and, d) to gain some insight in the distribution of epoxide and diol in the water and bead phases and the formulation parameters that have an effect thereon. Rhodospridium toruloides was immobilised in calcium alginate beads consisting of different combinations of alginate and CaCl2 concentrations. Best results were obtained with a combination of 0,5 % (m/v) alginate and 0,2 M CaC12. The immobilised cells exhibited lower initial activity. but more than 40 times the residual activity of that of the free cells after a 12-hour storage period. Both the immobilised and free cells exhibited an increase in reaction rate (V) with an increase in substrate concentration. An increase in the alginate concentration lead to the formation of smaller beads, but a decrease in enzume activity, while an increase in the CaCl2 solution concentration had no effect on bead diameter or enzyme activity. Epoxide diffused preferentially into the beads (± 96 %), and the diol into the water phase, which leads to the natural separation of the epoxide and the diol. The CaCl2 concentration affected epoxide diffusion with no effect on diol diffusion, which opens up the possibility to regulate the diffusion of epoxide into the beads. Although only a very small fraction of the epoxide inside the beads could be extracted, the alginate proved to be chirally selective for the (R)-epoxide, improving the reaction efficiency by increasing the % ee, of the epoxide extracted from the beads between 26 % and 43 %. The possibility to develop a system where the product is formed, purified and concentrated in a one-step reaction by extracting the product from the bead phase was clearly demonstrated. / Thesis (M.Sc. (Pharm.) (Pharmaceutical Chemistry))--Potchefstroom University for Christian Higher Education, 2003.

Pneumothorax, or a collapsed lung, is a serious medical condition resulting when air or fluid escapes the lung into the chest cavity and prevents the lung from inflating. Few viable means of sealing the damaged and leaking tissues are currently available, leading to longer hospital stays, multiple interventions, and increasing costs of care. The motivation of this dissertation is to engineer a novel polysaccharide-based therapeutic surgical sealant, which can be utilized to seal trauma-induced damage to the outer lining of the lung, i.e. pleura, preventing or reversing lung collapse to restore normal breathing function. The use of polysaccharides, such as alginate and hyaluronan, has become increasingly prevalent in biomedical and tissue engineering applications due to the ability to add functionality through chemical modification, allowing for tunable mechanical and physical properties. These hydrophilic polymer chains can be crosslinked to form hydrogels, which can retain large volumes of water and can mimic the properties of tissues found within the body. In this work, polysaccharide hydrogel sealants were engineered with well-regulated gelation and mechanical properties, and further modified to achieve adhesion to biological tissues. This was accomplished by mimicking the mechanical and physical properties of the complex tissues, and crosslinking the hydrogels in situ using a visible light-initiated system. Methacrylated alginate and oxidized alginate were successfully synthesized and utilized to fabricate adhesive sealant patches, which can adhere and seal damaged tissues in vivo. Methacrylation was implemented to allow covalent photo-crosslinking between adjacent polymer chains in solution. Here, a novel anhydrous chemistry was developed to allow for precise control over the degree of methacrylation and thus tune the mechanical properties of the resulting hydrogels by modulating the number of crosslinkable side-groups attached to the polysaccharide chain. To increase the adhesive properties of the resulting hydrogels, oxidation of the polysaccharide chain was subsequently implemented to form functional aldehyde groups capable of protein interactions through the formation of imine bonds on biological tissue surfaces. To test the performance of this multifunctional material, burst pressure testing was executed, revealing the relationship between the two distinct chemical modifications performed and the mechanical and adhesive properties of the resulting sealant. In addition, methacrylated alginate was utilized to synthesize therapeutic, drug-encapsulating hydrogel nanoparticles, which when incorporated within the polysaccharide-based surgical sealant allow for local drug release. The ability to control drug release at the site of application further broadens the potential uses of this surgical sealant patch and will be discussed further within this dissertation.

Neste trabalho foram estudados os efeitos causados pelo tratamento térmico na argila STx-1b-Li+ na condutividade de filmes argila/alginato de sódio. O argilomineral STx-1b foi submetido à substituição isomórfica do cátion Na+ por Li+ e posteriormente ao tratamento térmico em diferentes temperaturas. As argilas STx-1b-Li+ não tratada e tratada termicamente foram caracterizada por difração de raios-X (DRX) e termogravimetria (TG). As curvas TG mostraram que o argilomineral STx-1b-Li+ apresentou três perdas de massa que podem ser atribuídas à água adsorvida na argila, a água de hidratação dos íons Li+ e a água estrutural da argila. Para as argilas STx-1b-Li+ tratadas termicamente não foi observado a perda de massa associada à água quimicamente ligada aos contra-íons Li+. Estes resultados estão em concordância com os obtidos por DRX, onde observou-se uma diminuição no espaçamento interlamelar nas argilas tratadas termicamente. Em adição, foram preparados filmes de alginato de sódio com as argilas STx-1b-Li+ não tratada e tratada termicamente e estes foram caracterizados por calorimetria exploratória diferencia (DSC) e espectroscopia de impedância eletroquímica (EIE). As curvas DSC mostraram um aumento na temperatura de transição vítrea (Tg) dos filmes com o aumento da temperatura utilizada no tratamento das argilas. Este aumento nos valores de Tg é um indicativo que a mobilidade das cadeias diminuiu nos filmes polímero/argila que contém argilas tratadas em temperaturas mais elevadas. A espectroscopia de impedância eletroquímica (EIE) foi usada para avaliar-se a condutividade iônica dos filmes. Os resultados indicaram que os filmes contendo argilas que foram tratadas com temperaturas mais altas apresentaram menor condutividade. / In this work the effects caused by the heat treatment in STx-1b-Li+ clay on the conductivity of sodium alginate/clay were studied. The clay mineral STx-1b was submitted to isomorphous substitution of the Na+ for Li+ cation and subsequently to heat treatment at different temperatures. The STx-1b-Li+ clays untreated and heats treated were characterized by X-ray diffraction (XRD) and Thermogravimetric Analysis (TG). The TG curve showed that the clay mineral STL-1b-Li+ had three mass losses which can be attributed to adsorbed water in the clay, the water of hydration of the Li+ ions and structural clay water. To STx-1b-Li+ clays heat treated there were no mass loss associated to the water chemically bound to Li+ counter ions. These results are in agreement with those obtained by XRD, which it was observed a decrease in interlayer spacing in the heat treated clay. In addition, they were prepared sodium alginate films with STx-1b-Li+ clays untreated and heat treated and these films were characterized by Differential Scanning Calorimetry (DSC) and Electrochemical Impedance Spectroscopy (EIS). DSC curves showed an increase in glass transition temperature (Tg) of the films with temperature increasing used in the treatment of clays. This increase in Tg value is an indicative that the mobility of the chains had decrease in the polymer/clay films which contains heat treated clays at higher temperatures. The electrochemical impedance spectroscopy (EIS) was used to evaluate the ionic conductivity of the films. The results indicate that films containing clays which have been treated at higher temperatures had lower conductivity.