Dans cette étude, nous avons combiné les bonnes propriétés mécaniques de l'alliage de titane Ti6Al4V avec les excellentes propriétés biologiques apportées par le greffage d’un polymère « bioactif » le poly(styrène sulfonate de sodium) (poly(NaSS)). Le greffage chimique du poly(NaSS) réalisé à partir de la surface de l'alliage a permis de générer des biomatériaux « fonctionnalisés » et « bioactifs ». Sur ces substrats, la réponse de cellules ostéoblastiques de la lignée MC3T3-E1 a été étudiée en présence et en absence de protéines d’intérêt (seules ou en mélange). Nous avons pu mettre en évidence l’effet de ces protéines, de leur conformation et de leur compétitivité sur la réponse cellulaire (adhésion, étalement, différenciation). Dans des conditions de culture sans sérum, la seule présence du poly(NaSS) améliore la réponse cellulaire en augmentant l’adhérence, l’étalement et en prolongeant la viabilité cellulaires. Nous avons montré qu’en présence du poly(NaSS) la Fn joue un rôle majeur dans l'attachement précoce des cellules quel que soit le milieu de culture même « déplété » en certaines protéines. D’autre part nous avons également montré que le poly(NaSS) modifie la conformation des protéines adsorbées en augmentant l'exposition de leurs sites de liaison « actifs », tels que le peptide RGD dans la molécule Fn favorisanr ainsi l’adhésion et la fixation cellulaires par le biais des intégrines. Entre toutes les protéines étudiées, Col I a été identifiée comme la protéine qui stimule de manière la plus significative la minéralisation de la matrice ostéoblastique, en augmentant l'activité de la phosphatase alcaline et la production de phosphate et de calcium. Les surfaces greffées de poly(NaSS) pré-adsorbées du mélange protéique Fn & Col I favorisent l'expansion cytoplasmique des ostéoblastes, leur force d'attachement, leur différenciation et leur minéralisation. La compétitivité des protéines Fn, Col I et BSA protéine a également été étudiée. En résumé, le poly(NaSS) greffé sur des surfaces de Ti6Al4V propose une solution prometteuse pour l'ostéointégration rapide des biomatériaux, avec des applications possibles dans les domaines orthopédiques et dentaires. / In this investigation, we combined the good mechanical properties of the titanium (Ti) alloy Ti6Al4V with the biological properties, namely bioactivity, of the polymer poly(sodium styrene sulfonate) (poly(NaSS)). By chemically grafting the poly(NaSS) on the surface of the Ti alloy we generated biofunctionalized biomaterials. On these substrates, the MC3T3-E1 osteoblast-like cells response was followed in the presence and absence of individual proteins and important information about the competitive behavior of proteins and their effect on the cell development was uncovered. In serum free medium conditions, poly(NaSS) influenced positively the cells response, by enhancing their attachment strength and by extending their viability and inherent morphology. Fn together with poly(NaSS) was found to play a major role in the cell early attachment, even when in double depleted medium. It was also seen, that poly(NaSS) alters the proteins conformation by increasing the exposure of active binding sites, such as the RGD peptide in the Fn molecule, and this way promoting integrin-mediated cell attachment. Between all proteins, Col I was found to stimulate more significantly the osteoblast-like cells matrix mineralization, by increasing the alkaline phosphatase activity and the calcium and phosphate productions. Grafted surfaces pre-adsorbed with Fn & Col I mixtures promoted the cell cytoplasmatic expansion, attachment strength, differentiation and mineralization. The competitive behavior of Fn and Col I was seen to prevail over BSA. In summary, the poly(NaSS) together with the Ti6Al4V material offers a promising solution for fast biomaterial osteointegration to be used in the orthopedic and dental fields.

The purpose of this research was to investigate the surface modifications that take place during the machining of NiTi SMA and Ti-6Al-4V with micro-EDM. This was done by creating an array of blind holes and micro-patterns on both work-pieces. To analyze the machined surface and investigate the results, scanning electron microscope (SEM), energy dispersive X- ray spectroscopy (EDS) and X-ray diffraction (XRD) techniques were employed. In addition, the effects of various operating parameters on the machining performance was studied to identify the optimum parameters for micro-EDM of NiTi SMA and Ti-6Al-4V. Recently, aerospace and biomedical industries have placed a high demand on nonconventional machining processes, which can be used to machine high strength and hardto- cut materials such as Titanium alloys, Shape Memory Alloys (SMA) and Super Alloys. Electrical Discharge Machining (EDM) is one of the non-traditional technologies that remove materials from the workpiece through a series of electrical sparks that occur between the workpiece and cutting tool with the presence of dielectric liquid. Obtaining smooth and defect-free surfaces on both workpieces was one of the challenges due to the re-solidified debris on the machined surface. The experimental results showed that there was significant amount of re-casting and formation of resolidification of debris on the Ti surface after machining. On the other hand, the surface generated in NiTi SMA were comparatively smoother with lesser amount of resolidified debris on the surface. By analyzing the results from XRD and EDS, some elements of electrode and dielectric materials such as Tungsten, Carbon and Oxygen were observed on NiTi and Ti surface after machining. In the study of effect of operating parameters, it was found that the voltage, capacitance and tool rotational speed had significant effect on machining time. The machining time was reduced by increasing the voltage, capacitance and tool rotational speed. The machining time was found to be comparatively higher for machining NiTi SMA than Ti alloy. Comparing all the parameters, the voltage of 60 V, capacitance of 1000 PF, and tool rotational speed of 3500 RPM were selected as optimum parameters for this study. Although signs of tool electrode wear and debris particles on the machined surface were observed for both workpieces during the micro-EDM process, Ti alloy and NiTi SMA could be machined successfully using the micro-EDM process.

Electrical Discharge Machining (EDM) is a non-traditional machining process that uses hundreds of thousands of minute electrical sparks per second to machine any electrically conductive material, no matter the hardness or how delicate it is. EDM allows a much greater range of design possibilities, unconstrained from the traditional machining processes, in which material is removed mechanically by either rotating the cutting tool or the work piece. Shapes that were impossible to machine by any other method, such as deep, precision, square holes and slots with sharp inside corners, are readily produced. It provides accurate geometries in high- aspect ratio holes and slots, blind undercuts, small holes adjacent to deep sidewalls, and complex cuts in thin, fragile parts. Micro-EDM is a growing form of manufacturing and will continue to expand within various production fields. Micro-EDM is especially attractive for the applications where the cutting time is minimal, but precision and accuracy are maximized. Micro- EDM is a non-traditional cutting process, which consistently produces ultra-precise holes with fine surface finishes and better roundness, while holding extremely close diameter tolerances. The process could be an excellent problem-solving tool for configurations that are difficult or impossible to produce using conventional machining processes. This study presents a comparative experimental investigation on the micro-EDM machinability of difficult-to-cut Ti-6Al-4V and soft brass materials. As both materials are electrically conductive, they were machinable using the micro-EDM process irrespective of their hardness. The machining performance of the two materials was evaluated based on the quality of the micro-features produced by the micro-EDM process. Both blind and through micro-holes and micro-slots were machined on brass and Ti-6Al-4V materials. The quality of micro-features was assessed based on the shape accuracy, surface finish and profile accuracy of the features. Finally, the arrays of micro-features were machined on both materials to compare the mass production capability of micro-EDM process on those materials.

Submitted by Bruna Carolina Costa (prabrunah@hotmail.com) on 2018-06-17T15:27:22Z No. of bitstreams: 1 Tese Final - CostaBC.pdf: 9813307 bytes, checksum: 06e43540e98bad04c9faaccaa3e9e5c9 (MD5) / Approved for entry into archive by Lucilene Cordeiro da Silva Messias null (lubiblio@bauru.unesp.br) on 2018-06-18T18:45:24Z (GMT) No. of bitstreams: 1 costa_bc_dr_bauru.pdf: 9671307 bytes, checksum: b57db2112606e04abdeb6cef0449e963 (MD5) / Made available in DSpace on 2018-06-18T18:45:25Z (GMT). No. of bitstreams: 1 costa_bc_dr_bauru.pdf: 9671307 bytes, checksum: b57db2112606e04abdeb6cef0449e963 (MD5) Previous issue date: 2018-04-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Dentre os biomateriais metálicos, largamente empregados pela indústria biomédica, o titânio (Ti) e suas ligas, principalmente o sistema Ti-6Al-4V (responsável por 45% da produção total de titânio como biomaterial) representam a principal escolha para a confecção de implantes ortopédicos e dentários. No entanto, processos de degradação (corrosão, desgaste e tribocorrosão) atuantes sobre estas ligas podem ocasionar a liberação de partículas e íons metálicos (comumente referidos produtos de desgaste ou debris), o que pode representar uma situação perigosa in vivo. Neste contexto, as propriedades físico-químicas dos produtos de desgaste irão influenciar fortemente o tipo e intensidade das respostas de um organismo vivo após sua exposição aos mesmos. De forma geral, a interação de tais produtos com as células dos tecidos adjacentes ao implante e do sistema imune pode desencadear processos de sinalização, nomeadamente em termos da produção e liberação de citocinas pró-inflamatórias, conduzindo a osteólise (reabsorção óssea) e consequente falha do implante. Ademais, muitas preocupações têm sido levantadas com relação à liberação de partículas e íons compostos pelos elementos alumínio e vanádio. Alternativamente, novas ligas de titânio isentas da adição destes elementos têm sido propostas nos últimos anos, dentre as quais podemos citar, por exemplo, a liga Ti-15Zr-15Mo. Neste trabalho, foram avaliados (in vitro), a partir de um modelo de células de camundongo, os possíveis efeitos relacionados à exposição de íons vanádio às células dos tecidos ósseo e conjuntivo (fibroblastos e osteoblastos). Ademais, a especiação iônica para determinação dos íons vanádio predominantemente relacionados aos resultados obtidos também foi realizada. Complementarmente, a avaliação do comportamento com relação à tribocorrosão para duas ligas de titânio (Ti-6Al-4V e Ti-15Zr-15Mo), a produção e caracterização de partículas de desgaste a partir destas ligas e avaliação dos efeitos relacionados à exposição de tais partículas às células do tecido ósseo (osteoblastos) humano, nomeadamente em termos de viabilidade celular e produção de citocinas pró-inflamatórias, também foram propostas. De acordo com os resultados obtidos, foi possível verificar que as espécies iônicas de vanádio predominantemente dissolvidas nos meios de cultura utilizados para os experimentos in vitro com os osteoblastos e fibroblastos de camundongo foram essencialmente vanadatos, nomeadamente H2VO4- e HVO42-. Verificou-se também que a interação destas espécies iônicas com as células das linhagens celulares testadas, principalmente fibroblastos, pode causar uma diminuição significativa em viabilidade para concentrações próximas aquela possível ser encontrada in vivo em pacientes que apresentam mau funcionamento de seu dispositivo médico baseado na liga Ti-6Al-4V. Para as partículas de desgaste geradas a partir de ensaios de tribocorrosão sobre as ligas Ti-6Al-4V e Ti-15Zr-15Mo foram verificadas características semelhantes com relação à morfologia e a capacidade de preservar a composição e estrutura cristalina do material a partir do qual são geradas. No entanto, diferenças significativas em termos de tamanho foram observadas. Por fim, verificou-se também que a interação das partículas de desgaste obtidas (ambas as composições) com células do tecido ósseo humano, in vitro, pode provocar a diminuição da viabilidade ou (possivelmente) alterações no metabolismo celular, além de conduzir a um aumento na produção das citocinas pró-inflamatórias interleucina-6 e prostaglandina E2. / Among the metallic biomaterials, widely used in the biomedical industry, titanium (Ti) and its alloys, mainly the Ti-6Al-4V system (responsible for 45% of the total titanium production as biomaterial) represent the main choice for orthopedic and dental implants’ manufacturing. However, degradation processes (corrosion, wear and tribocorrosion) acting on these alloys may lead the release of metallic particles and/or ions (also referred as wear products or debris), and this may represent a dangerous situation in vivo. In this context, the wear products’ physical-chemical properties will strongly influence the type and intensity of the living organism responses after their exposure to them. In general, these products’ interaction with the implants’ surrounding tissues and immune system cells may trigger signaling processes, particularly in terms of the proinflammatory cytokines production and release, leading to osteolysis (bone resorption) and consequent implant loosening. Additionally, many concerns have been raised regarding the release of particles and ions composed by aluminum and vanadium. Alternatively, new vanadium and aluminum-free titanium alloys have been proposed in recent years, among which it is possible to mention, for example, the Ti-15Zr-15Mo alloy. In this work, the possible effects related to the vanadium ions exposure to bone and connective tissue cells (fibroblasts and osteoblasts) were evaluated (in vitro), from a mouse cells’ model. Also, ionic speciation analyzes were also performed in order to determine the vanadium ions related to the obtained results. Complementarily, the tribocorrosion behavior evaluation of two titanium alloys (Ti-6Al-4V and Ti-15Zr-15Mo), the production and characterization of wear particles generated from these alloys and the evaluation of the possible effects related to these particles exposure to human osteoblasts (particularly in terms of cell viability and proinflammatory cytokines production) were also proposed. According to the obtained results, it was possible to verify that the vanadium ionic species predominantly dissolved in the culture media used for the in vitro experiments with mouse osteoblasts and fibroblasts were essentially vanadates, namely H2VO4- and HVO42-. It has also been found that the interaction of such ionic species with the tested cells lines, mainly fibroblasts, may lead to a significant decrease in cell viability at concentrations close to that possible to be found in vivo for patients who present malfunctioning of their medical device based on Ti-6Al-4V alloy. Regarding the wear particles generated from tribocorrosion assays on Ti-6Al-4V and Ti-15Zr-15Mo alloys, similar characteristics were verified, mainly in morphology and the ability to preserve the chemical composition and crystal structure of the material from which are generated. However, significant differences in size were observed. Finally, it has also been found that the interaction of the obtained wear particles (both compositions) with human bone tissue cells, in vitro, may be related to decreased viability or (possibly) changes in cellular metabolism, in addition to leading to an increased production of the interleukin-6 and prostaglandin E2 proinflammatory cytokines / 88887.122946/2016-00