No description available.

No description available.

2-Methacryloyloxyethyl Phosphorylcholine is an interesting biocompatible monomer. An improved method for the synthesis of poly(MPC) and its copolymers using Reversible Addition-Fragmentation chain Transfer (RAFT) has been discussed in the first part of the thesis. Previous reports related to the synthesis of MPC homopolymers and copolymers in aqueous medium are found to be less effective because of the hydrolysis of chain transfer agent in water. Hydrolysis of chain transfer agent results in the loss of active chain ends thereby, reducing control over polymerization and increasing the polydispersity of resulting polymers. Therefore, in this work MPC polymers were synthesized by RAFT using methanol as solvent. This method of synthesis produced polymers having controlled molecular weights as well as narrow polydispersities. In the second part of the work, methoxydiethylene glycol methacrylate (MeODEGM)-MPC based thermo-responsive core-shell nanogels were synthesized for use in protein encapsulation and release. The size of the nanogels was controlled by varying the concentration of cross-linker. The nanogels were synthesized using an acid degradable crosslinker which helped in the release of encapsulated protein at acidic pH. The effect of various parameters on encapsulation efficiency of proteins was studied and it was found that apart from the size of protein, the cross-linker concentration of nanogel also affected the amount of protein encapsulated. / Chemical Engineering

The aim of this diploma thesis is the preparation of liposome nanoparticles enriched with PHA and PHA nanofibers. The nanostructures served to encapsulate extracts of lipophilic and hydrophilic nature. The characterization of the properties of nanostructures such as polydispersity, size, colloidal stability, long-term stability after exposure to various environments such as seawater, water from the Brno dam and tap water, and finally the cytotoxicity of fibers with extracts was addressed. The theoretical part is focused on different types of water, human skin, coffee and subsequently carotenoids. It continues by describing of possibilities of extraction and preparation of lipophilic and hydrophilic extracts and possibilities of their determination is discussed. Finally, it describes the possibilities of preparation and characterization of PHA based nanomaterials. The practical part deals with the preparation of liposome particles and fibers enriched with PHA with encapsulated extracts, their characterization, and their subsequent exposure to various environments. Monitoring of their long-term stability was carried out, but the release of the encapsulated extracts into the environment to which the nanoparticles and nanofibers were exposed was also measured. Finally, the interaction of nanofibers with live HaCaT cells was monitored, and cytotoxicity assays determined the viability of the cells after interaction with the nanofibers.

No description available.

Nisin is a naturally occurring food antimicrobial that inhibits many Grampositive pathogens, including Listeria monocytogenes, a bacterial pathogen responsible for ~500 deaths in the U.S. annually. Factors known to counteract the nisin activity in a food matrix include: antimicrobial interaction with food components, insolubility, protease inactivation, and target cell-driven envelope modifications. Encapsulating nisin in liposomes can help protect nisin functionality by regulating its introduction to the external environment. The objectives of this study were to determine the encapsulation efficiency (%EE) of nisin within liposomes as a function of encapsulation method and the capacity of liposomal nisin to inhibit L. monocytogenes in fluid milk. Phosphatidylcholine (PC) and phosphotidyl-DL-glycerol (PG) were used to prepare three lipid molar formulations: PC, PC/PG 7:3, and PC/PG 6:4 (mol.%). Liposomes were formulated to entrap the self-quenching fluorophore calcein and nisin. Unencapsulated analyte was removed via size-exclusion chromatography, and percent EE was determined. To determine antilisterial activity of liposomes, fluid milk samples containing L. monocytogenes (4 log10 CFU/mL) in combination with liposomal or unencapsulated nisin at 50 IU/mL were mixed and aerobically stored at 5 degrees C and 20 degrees C. Surviving L. monocytogenes were enumerated via plating on a non-selective microbiological medium after 0, 1, 3, 6, 12, 24, 48, and 72 hours of incubation. Encapsulation of nisin via extrusion resulted in a mean EE% of 84.20%, 77.33% and 80.78% for PC, PC/PG 7:3, and PC/PG 6:4 liposomes, respectively. Freeze-thaw cycling formed liposomes without detectable fluorophore entrapment. L. monocytogenes populations grew to 5 log10 CFU/mL after 72 hours at 5 degrees C and 8 log10 CFU/mL at 20 degrees C after 48 hours. Unencapsulated nisin exerted statistically greater inhibition of Listeria in skim milk compared to liposomal nisin, regardless of incubation temperature. No statistically significant differences in Listeria populations exposed to free or encapsulated nisin in whole milk were observed at either incubation temperature. Results indicate storage temperature and presence of milk fat exert greater influence then nisin delivery (free vs. encapsulated) over Listeria inhibition. Further research is needed to confirm these findings and develop more effective means of liposome entrapment of nisin for the inhibition of foodborne bacterial pathogens.

La technique puce retournée pour l’encapsulation des puces est largement utilisée dans l’industrie, mais présente de nombreux défis. Cette technique requiert que les matériaux utilisés subissent de hautes températures (250°C). Or, le silicium et le substrat organique ont des coefficients d’expansion thermique (CET) très différents. Donc, ces températures et la différence de CET induisent des contraintes sur la puce. Ces contraintes affectent les performances électriques de la puce et peuvent provoquer la fissuration de celle-ci. L’humidité à l’intérieur du module s’ajoute aux problèmes. Elle corrode les interconnexions puis facilite la formation de trous dans l’époxy utilisé pour augmenter la cohésion mécanique entre la puce et le substrat. Jusqu’à maintenant des jauges de déformations sur silicium ont été réalisées. Bien que les facteurs de jauges obtenus soient grands (100), cette technique basée sur la théorie des semi-conducteurs nécessite que la surface dédiée à la circuiterie soit remplacée par la jauge. Actuellement, aucune technique ne permet de mesurer efficacement les déformations sur la surface d’une puce sans modifier sa circuiterie. Ainsi, l’objectif est de développer une jauge de déformation et d’humidité portable constituée de nanotubes de carbone. Cette jauge sera positionnée directement sur la couche de polyimide, elle-même située sur la circuiterie. Les propriétés piézorésistives des nanotubes ainsi que leurs dimensions sont des atouts pour la conception de ces jauges micrométriques. Globalement, le projet se sépare en trois volets : étude et optimisation des films de nanotubes, fabrication de capteurs prototypes puis intégration des capteurs dans le module. Le premier volet sert à déterminer la méthode optimale de dépôt des nanotubes et le type de nanotubes préférables. La fabrication de capteurs prototypes permet de définir un procédé de microfabrication et de calibrer en déformation, température et humidité.

Good reliability of the encapsulation system of Photovoltaic (PV) modules is crucial to ensure the long-term performance of PV modules. A carefully controlled lamination process is required to produce a reliable encapsulation system. To date, the influences of different lamination conditions on the reliability of the encapsulation system are poorly understood. To predict the performance of the encapsulation system, the correlation of the reliability of the encapsulation system with various stress levels is required, which is poorly developed. This thesis improves the understanding of these issues by investigating the correlation of different lamination conditions with the reliability of the encapsulation system and the degradation of adhesion strength under variable damp-heat conditions. The influence of the curing temperature and curing time on the long-term reliability of the encapsulation system is investigated from various viewpoints such as curing level of EVA, chemical and optical stability of EVA and adhesion strength within the encapsulation system. The correlation of curing level and lamination quality has been identified. The effects of over-curing are demonstrated. Results show that the chemical stability, optical stability and the adhesion strength between encapsulant and backsheet increases with the increasing curing level. However, the best long-term adhesion performance at the glass-encapsulant interface is obtained at lower gel content. Too high curing can cause problems of bubble generation, discoloration and unstable interfaces. Among those identified degradation phenomena, interfacial adhesion strength demonstrates the fastest and the largest degradation. The reliability of the adhesion strength is further examined under different stress levels. Among different environmental stress factors, moisture is considered to cause the greatest problems of adhesive interfacial stability. Therefore, the adhesion strength is investigated under different damp-heat conditions. A methodology is developed that can be used to model the adhesion degradation induced by moisture at different humidity and temperature conditions. To do so, a stress model is established which enables quantitative description of the moisture related stresses on PV modules. Based on this model, an exponential correlation is established between the adhesion strength and the humidity and temperature levels. This enables the comparison of adhesion strength of PV modules operating at different humid environments.

Ce sujet se situe dans le cadre de la mise au point de systèmes de délivrance de composés thérapeutiques ou d’imagerie, c’est à dire d’objets qui doivent transporter des composés dans un organisme et posséder une spécificité pour une zone à traiter ou à imager. Les objectifs de mon travail de thèse étaient l’addition d’une spécificité aux liposomes grâce à la liaison ou l’utilisation de protéines dérivées de l’Annexine 5 (Anx5) et l’encapsulation dans l’espace interne des vésicules de composés permettant le suivi de ces vecteurs. Nous avons tout d’abord mis au point des liposomes pour lesquels l’Anx5 est couplée à l’extrémité d’un lipide-PEG et sert d’élément d’adressage vers des cellules en apoptose. La liaison Anx5 / lipide-PEG a été caractérisée par SDS-PAGE de façon à contrôler la densité de ligand en surface des vésicules. L’influence de cette densité de ligand sur l’efficacité de liaison des vecteurs à des membranes cibles et sur l’agrégation des vésicules a été évaluée par QCM-D et DLS. Il apparait qu’une densité de 60 Anx5 / liposome est un optimum vis-à-vis de ces facteurs. Enfin l’encapsulation de fluorophores a permis d’imager l’interaction des liposomes-Anx5 avec des cellules en apoptose. Pour former des magnétoliposomes nous avons mis au point et caractérisé l’encapsulation de particules d’oxyde de fer dans des liposomes neutres et anioniques. La procédure d’encapsulation passive ainsi que l’influence de la charge membranaire négative et la stabilité des magnétoliposomes ont été évaluées. Le nombre de particules d’oxyde de fer par vésicule a été déterminé par dosages et l’aspect des liposomes a été examiné par cryomicroscopie électronique à transmission. Un maximum d’environ 50 particules par liposome a été encapsulé dans des vésicules de 100nm de diamètre. La présence de lipides anioniques limite l’efficacité d’encapsulation et favorise la déstabilisation des magnétoliposomes. Enfin, la liaison d’anticorps en surface des liposomes grâce à l’Anx5ZZ a été caractérisée et optimisée de façon à utiliser ces anticorps comme éléments d’adressage pour cibler deux pathologies : l’athérosclérose et l’inflammation. La composition lipidique a été optimisée pour encapsuler de façon stable des fluorophores tout en liant des Anx5. Les expériences de caractérisation de la fonctionnalisation par DLS et FRET nous ont conduits à choisir une séquence pour l’association des anticorps qui consiste a associer les anticorps aux Anx5ZZ dans un premier temps à lier ce complexe en surface des liposomes. Deux anticorps ont été utilisés pour vérifier les capacités d’adressage des vecteurs vers des cibles biologiques, tout d’abord ex vivo sur des modèles de plaques d’athérome puis ex et in vivo sur des rats présentant des zones d’inflammation. L’ensemble de ces travaux ont donc consistés à mettre au point des liposomes fonctionnalisés avec des dérivés d’Anx5 et encapsulant des éléments dans l’espace interne des vésicules. Ces vecteurs ont étés utilisés pour imager des cibles biologiques. / This subject is in the framework of drug or imaging agent delivery system. This object must carry compound in an organism and selectively recognize a target area. The aims of my work were to add a targeting element to liposomes by use of Anx5 derivative and to encapsulate imaging compound inside the aqueous inner space. First we designed Anx5-bearing liposomes with the Anx5 protein covalently linked at the distal end of a PEG-lipid and used as targeting element. Anx5 conjugation was monitored by SDS-PAGE in order to control Anx5 density on the liposome surface. The influence of ligand density on the efficiency of binding to target membranes and on solutions dispersity was assessed by QCM-D and DLS. A density of 60 Anx5 / liposomes ensure the best target recognition efficiency and dispersity. Finally fluorescent dyes encapsulation was used to image the interaction between Anx5 bearing liposomes and apoptotic cells. To prepare magnetoliposomes we have synthesized and characterized the encapsulation of iron oxide nanoparticle inside neutral and anionic liposomes. The passive encapsulation procedure, the influence of the negative charge and the magnetoliposome stability were evaluated. The number of particle / vesicle was assayed and the liposomes aspect was examined using cryoelectron microscopy. An average of 50 particles / liposomes was encapsulated inside 100nm vesicles. Anionic lipids limit the encapsulation efficiency and promote liposomes destabilization. Finally the use of Anx5ZZ to anchor antibodies on the liposomes surface was characterized and optimized to use antibodies as homing device to target two diseases: atherosclerosis and inflammation. Lipid composition was optimized to stably entrap fluorescent dyes while Anx5 are bound on the membrane. To functionalize the vector, DLS and FRET experiment leads us to choose a sequence that consists in associating antibodies to the Anx5ZZ in a first time and then binding this complex on the liposome surface. Two antibodies were used to address the liposome toward biological targets, ex vivo on atherosclerosis models and in vivo on rats bearing inflammation areas.

Droplet-based microfluidics can be used to enhance stem cell-based therapy by creating cell-laden hydrogel encapsulations to increase engraftment and retention while providing protection from immune responses caused by the host environment. Current research involves gaining better control over therapeutic mechanisms and one focus is to understand the mechanisms behind cell egress. Control over egress is vital to determining how long cells remain in proximity to the therapeutic target. We propose a microfluidic platform capable of encapsulating cells in two subsequent steps in order to create a double emulsion structure around the cell. In this project, hydrogel-in-hydrogel microdroplets are successfully manufactured without the presence of an intermediate oil layer and are used to observe model NIH 3T3 cell egress. In studying cell egress from singly or doubly encapsulated microcapsules, we are able to better understand the mechanisms that drive egress. Specifically, we hypothesize that cells egress when close to the edge of the microcapsule. In a double emulsion, cells are naturally located away from the edge and closer to the center. Results show that double emulsion microdroplets significantly reduce cell egress but do not eliminate it.