Made available in DSpace on 2014-06-11T19:31:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-02-06Bitstream added on 2014-06-13T19:40:59Z : No. of bitstreams: 1 leles_jlr_dr_araca.pdf: 1159504 bytes, checksum: bec692179cdbbe9f9b34ee0da4cdcfc8 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Há grande interesse no desenvolvimento de meios para manutenção ou recomposição alveolar visando a instalação de implantes osseointegráveis. No presente estudo o processo de reparo alveolar após implante de vidro bioativo (Biogran®) foi avaliado histologicamente. Quatro macacos-prego (Cebus apella) adultos tiveram seus incisivos superiores extraídos e os alvéolos preenchidos com vidro bioativo - Biogran® (Grupo Tratado, n=6 alvéolos) ou por coágulo sangüíneo (Grupo Controle, n=4 alvéolos). Aos 100 dias pós-operatórios os animais foram sacrificados e os espécimes removidos para processamento histológico. Observou-se que os alvéolos do Grupo Controle apresentavam tecido ósseo maduro distribuído irregularmente em trabéculas esparsas com grandes espaços medulares. Já no Grupo Tratado, encontravam-se preenchidos por uma rede de tecido ósseo neoformado com configuração lamelar e ampla ocupação alveolar. Os poucos fragmentos remanescentes do material foram vistos rodeados por tecido conjuntivo ou em contato direto com o tecido ósseo. Concluiu-se que o implante intra-alveolar de vidro bioativo favoreceu a neoformação óssea, atuando como agente osteocondutor. / Maintenance or reconstruction of alveolar process is a topic of great interest in oral rehabilitation with implants. The aim of this study was to investigate the histological features of alveolar wound healing in dental sockets grafted with bioactive glass. Four adult capuchin monkeys (Cebus apella) have their incisor teeth extracted and alveolus filled with particulate bioactive glass Biogran® (Test Group: n=6 alveolus) or blood coagulum (Control Group: n=4 alveolus). After 100 days, animals were sacrificed and specimens removed for histological processing. It was observed that Control Group presented mature neoformed bone irregularly distributed in few trabeculas with large medullar spaces. Alveolus of Test Group were filled with a net of lamellar neoformed bone. The few remaining particles of bioactive glass were surrounded by connective tissue or in close contact with bone tissue. It was concluded that intra-alveolar bioactive glass improved bone neoformation by osteoconductive action.

La modification d’oligonucléotides est un domaine attrayant de la chimie organique. De nombreuses études se sont intéressées à la génération de liens internucléosidiques artificiels à visée thérapeutique, diagnostic ou encore pour des applications en chimie prébiotique. Ce manuscript de thèse rapporte la synthèse et l’étude de biocompatibilité d’acides nucléiques modifiés à leurs extrémités 5’ par un acide boronique. Les comportement des oligomères boroniques a été évalué en présence de différentes classes d’enzymes telles que les ligases, les polymérases ou encore les phosphodiestérases. Les résultats de biocompatibilité obtenus en présence de ces enzymes nous ont permis d’utiliser ces acides nucléiques modifiés comme de réels outils de diagnostic pour réaliser de la détection de point de mutation ou encore de la détection de péroxynitrite in-cellulo. / The modification of oligonucleotides is an attractive field of organic chemistry. Many studies have focused on the generation of artificial internucleoside linkages for therapeutic, diagnostic or for applications in prebiotic chemistry. This thesis manuscript reports the synthesis and study of nucleic acids biocompatibility modified at their 5 'ends by a boronic acid function. The behavior of boronic oligomers was assessed in the presence of different classes of enzymes, such as ligases, polymerases or phosphodiesterases. The biocompatibility results obtained in the presence of these enzymes allowed us to use these modified nucleic acids as real diagnostic tools to achieve mutation point detection or detection of peroxynitrite in-cellulo.

<p>Today there are a vast number of medical devices in temporary or permanent contact with human tissues. Blood-biomaterial contact is known to trigger the complement system and results in generation of fluid phase anaphylatoxins C3a and C5a, and surface-bound C3b and iC3b. All these products together are able to attract and activate leukocytes and trigger release of inflammatory mediators leading to a systemic inflammation indirectly causing hemostatic problems and even organ failure. The aim of this study was to identify how complement is triggered on a biomaterial surface and to find ways to regulate this activation.</p><p>The finding that complement activation on biomaterials can be divided into initiation and amplification will facilitate regulation of complement activation biomaterial surfaces. This concept is also compatible with the two techniques to regulate complement activation on a surface.</p>

Chronic nerve recording and stimulation can be performed by means of nerve cuff electrodes in both animals and humans. These extraneural electrodes have been used not only for fundamental research but also for rehabilitation purposes as part of a neuroprosthetic device. They have therefore contributed to our knowledge of the nervous system and also allowed partial motor and sensory rehabilitation. However, the performance of existing nerve cuff electrodes remains limited and their designs must be improved. The main drawbacks of cuff electrodes are their poor selectivity and the morphological modifications they induce to surrounding tissue. Their selectivity is mainly dependant on the number of contacts which is limited by the hand-made manufacturing process. The morphological modifications are determined by the tissue-electrode interactions. A new spiral cuff nerve electrode is proposed to improve the selectivity and lessen the tissue reaction. The manufacture of this new electrode, based on photolithographic metal deposition technology, should allow for an increased number of contacts. Additionally, this electrode has self-sizing properties that potentially lowers the implant-induced tissue reaction. The present work aims to study the interactions between the electrode and implanted tissue in an attempt to better characterise the tissue reaction and to further control it. Firstly, the interactions between connective tissue and the laser-irradiated-platinum-metallised silicone rubber are assessed both with in vitro and in vivo methods. The cytocompatibility and biocompatibility of silicone is not altered by the platinum deposition process, suggesting that this new biomaterial can be used to manufacture cuff electrodes that can safely be implanted for chronic studies. The mechanical biocompatibility of spiral cuff nerve electrodes is then investigated by morphological, immunohistochemical and western-blots analyses. The peri-operative, acute and chronic events that are related to the implantation are studied. The results show that the commonly described fibrotic reaction surrounding the implant is preceded by an important early epineurial inflammation. Additionally, cytokines involved in this tissue reaction are identified and include the pro-inflammatory cytokine TNF-alpha and pro-fibrotic cytokine TGF-beta1. In continuation of the biocompatibility testing, cytokine neutralisation through monoclonal antibodies is proposed as a way to control some of the cuff electrode-induced tissue modifications. Immunohistochemistry and morphometry are used to demonstrate the feasibility of such a control. Results show that a single systemic injection of TNF-alpha neutralising antibodies is sufficient to reduce the early inflammatory reaction occurring in the epineurial compartment but not the subsequent fibrosis. The success of an implanted neuroprosthesis is fully dependant upon the interaction between the electrode and the surrounding tissue. This study suggests that, when trying to improve the design of an electrode, one should also consider the modulation of the tissue reaction as a convenient way to enhance the implanted electrode's long-term performance. / L'enregistrement et la stimulation chroniques de nerfs peuvent être réalisés au moyen d'électrodes neurales à manchon, aussi bien chez l'animal que chez l'homme. Ces électrodes extra-neurales ont été utilisées non seulement dans le cadre de recherches fondamentales mais aussi à des fins de réhabilitation au sein d'un dispositif neuro-prosthétique. Elles ont ainsi contribué à notre connaissance du système nerveux et ont parfois permis une restauration sensorielle et motrice partielle. Les performances des électrodes existantes demeurent cependant limitées et leur design doit être amélioré. Les principales faiblesses de ces électrodes à manchon sont leur sélectivité, insuffisante, et les modifications morphologiques qu'elles induisent au sein des tissus implantés. La sélectivité des électrodes dépend principalement du nombre de contacts que limite un procédé de fabrication manuel. Les modifications morphologiques sont, quant à elles, déterminées par les interactions entre les tissus et l'électrode. Une nouvelle électrode neurale, dite à manchon spiral, est proposée qui devrait accroître la sélectivité et réduire la réaction tissulaire. La fabrication de cette nouvelle électrode, basée sur la technologie de déposition photolithographique de métaux, devrait permettre d'augmenter le nombre de contacts. De plus, en raison de son aptitude à s'adapter au diamètre du nerf, cette électrode devrait potentiellement limiter la réaction tissulaire induite par l'implant. Le but de ce travail est d'étudier les interactions entre l'électrode et les tissus implantés afin de mieux caractériser la réaction tissulaire et, ultérieurement, la contrôler. Dans un premier temps, les interactions entre les tissus conjonctifs et le silicone après son irradiation au laser et sa métallisation sont testées au moyen de méthodes in vitro et in vivo. La cyto-compatibilité et la biocompatibilité du silicone ne sont pas altérées pas le procédé de dépôt du platine. Ceci suggère que ce nouveau biomatériau convient à la manufacture d'électrodes à manchon qui pourront être implantées chroniquement de façon sûre. Dans un second temps, la biocompatibilité mécanique des électrodes à manchon spiral est examinée au moyen d'analyses morphologiques, immunohistochimiques et de western-blots. Les événements péri-opératoires, aigus et chroniques liés à l'implantation sont étudiés. Les résultats montrent qu'une importante réaction inflammatoire précoce précède la réaction fibrotique autour de l'électrode, classiquement décrite après une implantation. De plus, une partie des cytokines impliquée dans la réaction tissulaire est identifiée: la cytokine pro-inflammatoire TNF-alpha et la cytokine pro-fibrotique TGF-beta1. Dans la continuité des études de biocompatibilité, la neutralisation de cytokine au moyen d'anticorps monoclonaux est proposé comme moyen de contrôle de modifications tissulaires induite par l'électrode à manchon. L'immunohistochimie et la morphométrie sont utilisées pour démontrer la possibilité d'un tel contrôle. Le résultats montrent qu'une seule injection systémique d'anticorps anti-TNF-alpha est suffisante pour réduire la réaction inflammatoire précoce dans le compartiment épineurial mais pas la fibrose subséquente. Le succès d'une neuroprothèse implantable dépend entièrement des interactions entre l'électrode et les tissus environnants. Cette étude suggère que, lors des tentatives d'amélioration du design des électrodes, la modulation de la réaction tissulaire devrait être considérée comme un moyen aisé d'augmenter les performances à long terme des électrodes implantées.

Today there are a vast number of medical devices in temporary or permanent contact with human tissues. Blood-biomaterial contact is known to trigger the complement system and results in generation of fluid phase anaphylatoxins C3a and C5a, and surface-bound C3b and iC3b. All these products together are able to attract and activate leukocytes and trigger release of inflammatory mediators leading to a systemic inflammation indirectly causing hemostatic problems and even organ failure. The aim of this study was to identify how complement is triggered on a biomaterial surface and to find ways to regulate this activation. The finding that complement activation on biomaterials can be divided into initiation and amplification will facilitate regulation of complement activation biomaterial surfaces. This concept is also compatible with the two techniques to regulate complement activation on a surface.

Mesoporous silica particles offer great potential benefits as vehicles for drug delivery and in other biomedical applications. They present a high loading capacity due their ordered and size-tuneable pores that allow molecules to be loaded and released. In addition, they offer the possibility to enhance oral bioavailability of drugs with limited aqueous solubility and to protect pH sensitive drugs from the acidic conditions in the stomach on their way to the intestine. The aim of this thesis was to evaluate the biocompatibility and effects of mesoporous silica particles on immunocompetent cells. Subsequently, two potential life sciences applications were investigated: as adjuvants and as weight reduction agents. Adjuvants are used in vaccines in order to enhance the immunological response towards attenuated and poorly immunogenic antigens. Their function can be mediated through dendritic cells which have a central role in the control of adaptive immunity including immunological memory. Our results show that different types of mesoporous silica particles were able to tune the development of T cells both in human cell cultures and in mice. In contrast to the approved adjuvant alum (aluminium salts) which is a specific inducer of Th2-type immune responses, the particles induced more Th1-like responses, which may be desired in vaccines against allergy and intracellular pathogens such as viruses. Particle exposure to macrophages did not affect their cell function which is crucial for tissue homeostasis, wound repair and in prevention of autoimmune responses. Likewise, the cytokine secretion was not affected, which suggest that macrophages would not modulate the immune response towards the particles. Furthermore, mesoporous silica particles were highly tolerated at daily oral administrations of up to 2000 mg/kg doses for some of the materials prepared. Large pore mesoporous silica particles were shown to act as weight and body fat reduction agents without other observable pathological signs when administered in the diet of obese mice. Together; those results are promising for the development of mesoporous silica as drug delivery systems and adjuvants for oral administration of drugs or vaccines. Additionally, large pore mesoporous silica materials are potential agents for the treatment of obesity.

Fibroin is a biopolymer obtained from the cocoons of the Bombyx mori silkworm that offers many unique advantages. In this thesis work, fibroin was processed into a regenerated film and examined for potential biomaterial applications. The adsorption of bovine serum albumin onto the fibroin film was investigated to examine the biocompatibility of the film, and it was found that BSA adsorption capacity increased with an increase in BSA concentration. At 10 mg/mL of BSA, the BSA sorption reached 0.045 mg/cm2. This level of BSA is indicative of good blood compatibility and biocompatibility of the fibroin. The gas permeabilities of oxygen, nitrogen, and carbon dioxide were tested for potential applications in contact lenses and wound dressings. Over a pressure range of 70 – 350 psig, the permeability of oxygen and nitrogen was 5 Barrer, while that of carbon dioxide ranged from 26 to 37 Barrer. The oxygen transmissibility of the fibroin films prepared in this study was on the low end required for use in daily wear contact lenses, but sufficient to aid the healing process for use in wound dressings. The permeability and diffusivity of four model drugs in the fibroin film was investigated for potential applications in controlled drug release. The permeability at higher source concentrations leveled out to 0.8 – 4.3 x 10-7 cm2/s depending on the drug tested. The diffusion coefficient determined from sorption experiments was approximately 1.8 x 10-9 cm2/s, while the diffusion coefficients from desorption experiments were determined to be 0.8 – 2.7 x 10-9 cm2/s. The magnitude of the drug permeability and diffusivity are consistent with many other controlled release materials, and the fibroin film showed good potential for use in controlled release.

The aim of this study was to investigate the microstructure, microhardness and biocompatibility properties of nano hydroxyapatite (HA) doped with a constant yttrium (Y3+) and varying fluoride (F-) compositions. HA was synthesized via precipitation method and sintered at 1100&amp / #61616 / C for 1 hour. Increased densities were achieved upon Y3+ doping while F- doping led to a decrease in densities. For structural analysis, XRD, SEM and FTIR spectroscopy examinations were performed. No secondary phases were observed in XRD studies upon doping. Lattice parameters decreased due to substitutions of ions. In SEM analysis, addition of doping ions was observed to result in smaller grains. In FTIR analysis, in addition to the characteristic bands of HA, novel bands indicating the substitution of F- ions were observed in F- ion doped samples. The highest microhardness value was obtained for the sample doped with 2.5%Y3+, 1%F-. Increased F- ion contents resulted in decreased microhardness values. For biocompatibility evaluation, in vitro tests were applied to the materials. MTT assay was performed for Saos-2 cell proliferation analysis. Y3+ and F- ion incorporation was found to improve cell proliferation on HA discs. Cells were found to attach and proliferate on disc surfaces in SEM analysis. ALP assay showed differentiation of cells on the discs can be improved by doping HA with an optimum amount of F- ion. Dissolution tests in DMEM revealed that structural stability of HA was improved with F- ion incorporation. The material exhibiting optimum structural, mechanical and biocompatibility properties was HA doped with 2.5%Y3+, 1%F-.

published_or_final_version / Anatomy / Master / Master of Philosophy

published_or_final_version / Orthopaedics and Traumatology / Master / Master of Philosophy