Implantes de titânio têm sido extensivamente utilizados na ortopedia e na odontologia principalmente como substituto de elementos dentários ausentes. O titânio é um implante metálico de escolha por ser biocompatível, resistente à corrosão e desfavorecer reações imunológicas. A influência das características superficiais do titânio no comportamento e morfologia celular tem sido amplamente investigada, mas ainda existem questões em aberto sobre a sua interação com diferentes células em um microambiente. O objetivo do presente projeto foi caracterizar o comportamento de células provenientes do cordão umbilical humano em contato com uma superfície de titânio nanotexturizada em meio osteogênico e não-osteogênico. As células da sub-íntima da veia do cordão umbilical foram isoladas e colocadas em garrafas de cultura em meio essencial mínimo. Após a subconfluência, as células foram cultivadas em placas de 24 poços (n=5) em contato com discos de titânio comercialmente puro (cpTi) polidos (grupo controle) e com discos de titânio nanotexturizados através de condicionamento ácido (grupo Ti-nano). Os parâmetros avaliados foram: proliferação e viabilidade celular, quantidade de proteína total e atividade de fosfatase alcalina, além da detecção de nódulos mineralizados. Também foi realizada a expressão gênica quantitativa de genes relacionados à adesão e diferenciação por meio de PCR em tempo real. Todos os ensaios foram realizados em triplicata e os dados analisados através do teste estatístico Sigma Plot após aplicação de testes de normalidade e homogeneidade para p<0,05. / Titanium implants have been extensively used in orthopedics and dentistry, mainly as a replacement for missing teeth. Titanium is a metal implant of choice due to its high biocompatibility and corrosion resistance, as well as absence of immune response. The influence of titanium superficial characteristics on morphology and cell behavior has been broadly investigated, but there are still questions about the interaction between titanium and different types of cells in a microenvironment. The purpose of the present investigation is to characterize the behavior of cells from human umbilical cord vein in contact with a nanotextured titanium surface cultured on osteogenic and non-osteogenic medium. Cells were obtained from umbilical cord subintimal vein layer and cultivated in minimal essential medium. After subconfluence, cells were cultured in 24-well plates (n=5) on pure commercial polished titanium discs (control group) and on nanotextured titanium discs by means of acid etching. The evaluated parameters were cell viability, alkaline phosphatase activity as well as the detection of mineralized nodules. It was also performed quantitative gene expression of genes associated to adhesion and extracellular matrix by means of Real Time PCR. All the assays were performed in triplicate and the data obtained were analyzed by means of statistical test (Sigma Plot) after normality and homogeneity tests.

Les alliages ODS (Oxides Dispersion Strengthened), sont principalement étudiés pour leur capacité à répondre favorablement au cahier des charges de la fonction de gainage combustible pour les réacteurs nucléaire de type RNR-Na (Réacteur à Neutrons Rapides à caloporteur sodium). Elaborés par métallurgie des poudres, mécanosynthèse puis extrusion, ils affichent des propriétés mécaniques, et notamment en fluage, extrêmement intéressantes. Néanmoins, la voie élaboration utilisée induit une forte anisotropie microstructurale. Cette anisotropie se retrouve au niveau de leurs propriétés mécaniques et conduit à une fragilité dans le sens de sollicitation transverse. Le but de cette thèse est d'étudier l'évolution microstructurale de ces matériaux. Les aciers ODS présentent des microstructures ultra fines en termes de grains, de précipités, et de formation d'amas qui conduisent à de grandes difficultés pour en obtenir la recristallisation. De plus, les microstructures obtenues présentent souvent une recristallisation avec croissance anormale. De telles évolutions demandent des investigations à très fine échelle et ont été relativement peu examinées dans le domaine des alliages ODS. Il faut en effet être capable d'une étude structurale la plus quantitative possible de la microstructure des nanograins, ainsi que de la précipitation afin d'étudier les mécanismes d'interaction précipitation / joints de grain. Ceci n'est possible que par un couplage de différentes méthodes : la microscopie électronique en transmission (en particulier avec l'utilisation des outils récemment développés pour l'étude de la nanotexturation, i.e. ACOM-TEM); la diffusion centrale des neutrons ou des rayons X; et enfin la sonde atomique tomographique, à la fois pour apporter les informations sur la morphologie et la chimie des amas et nanoprécipités mais surtout sur la composition chimique aux joints de grains. A partir de l'identification des mécanismes contrôlant la croissance anormale, une modélisation permettant de prédire son apparition dans la microstructure est confrontée à cette caractérisation microstructurale poussée. Cette modélisation prête une attention particulière à la migration des joints de grains couplée à la diffusion et effets d'ancrage préférentiel des joints triples par les précipités ainsi qu'à l'énergie motrice stockée sous forme de densité de dislocation. / Oxide Dispersion Steels (ODS) alloys are mainly studied for their ability to fulfil the technical specifications required for Sodium Fast Reactor (SFR) fuel cladding application. Their processing involves powder metallurgy, mechanical alloying and extrusion. Therefore, despite their interesting mechanical creep properties, the extrusion processing involves a high microstructural anisotropy. These particular feature leads to poor mechanical properties in the transverse direction which are worsen by the occurrence of abnormal grain growth. Unfortunately, since internal pressure increases in the tube with the accumulation of gas fission products, the major stress component is precisely applied in the transverse direction. As a result, the material faces a critical risk of failure and control of the microstructure is a key issue. The aim of this thesis is to study the microstructural evolution of ODS ferritic steels. ODS ferritic steels show ultrafine microstructures in terms both grains and precipitates which made the recrystallization very difficult and allow for abnormal grain growth. To observe such evolutions, fine scale microstructure characterization are necessary. This is only possible by coupling different characterization methods: transmission electronic microscopy (in particular with the new developed tools for nanotexturation studies, i.e. ACOM-TEM); neutron and X-ray small angle scattering; and atomic probe tomography. Based on the mechanisms that lead to and control the abnormal grain growth, a model to predict the occurrence of abnormal grain growth is confronted to the experimental results. This model that takes a particular attention to the dislocation stored energy effect to adequately reproduce the observed characterization results.

Implantes de titânio têm sido extensivamente utilizados na ortopedia e na odontologia principalmente como substituto de elementos dentários ausentes. O titânio é um implante metálico de escolha por ser biocompatível, resistente à corrosão e desfavorecer reações imunológicas. A influência das características superficiais do titânio no comportamento e morfologia celular tem sido amplamente investigada, mas ainda existem questões em aberto sobre a sua interação com diferentes células em um microambiente. O objetivo do presente projeto foi caracterizar o comportamento de células provenientes do cordão umbilical humano em contato com uma superfície de titânio nanotexturizada em meio osteogênico e não-osteogênico. As células da sub-íntima da veia do cordão umbilical foram isoladas e colocadas em garrafas de cultura em meio essencial mínimo. Após a subconfluência, as células foram cultivadas em placas de 24 poços (n=5) em contato com discos de titânio comercialmente puro (cpTi) polidos (grupo controle) e com discos de titânio nanotexturizados através de condicionamento ácido (grupo Ti-nano). Os parâmetros avaliados foram: proliferação e viabilidade celular, quantidade de proteína total e atividade de fosfatase alcalina, além da detecção de nódulos mineralizados. Também foi realizada a expressão gênica quantitativa de genes relacionados à adesão e diferenciação por meio de PCR em tempo real. Todos os ensaios foram realizados em triplicata e os dados analisados através do teste estatístico Sigma Plot após aplicação de testes de normalidade e homogeneidade para p<0,05. / Titanium implants have been extensively used in orthopedics and dentistry, mainly as a replacement for missing teeth. Titanium is a metal implant of choice due to its high biocompatibility and corrosion resistance, as well as absence of immune response. The influence of titanium superficial characteristics on morphology and cell behavior has been broadly investigated, but there are still questions about the interaction between titanium and different types of cells in a microenvironment. The purpose of the present investigation is to characterize the behavior of cells from human umbilical cord vein in contact with a nanotextured titanium surface cultured on osteogenic and non-osteogenic medium. Cells were obtained from umbilical cord subintimal vein layer and cultivated in minimal essential medium. After subconfluence, cells were cultured in 24-well plates (n=5) on pure commercial polished titanium discs (control group) and on nanotextured titanium discs by means of acid etching. The evaluated parameters were cell viability, alkaline phosphatase activity as well as the detection of mineralized nodules. It was also performed quantitative gene expression of genes associated to adhesion and extracellular matrix by means of Real Time PCR. All the assays were performed in triplicate and the data obtained were analyzed by means of statistical test (Sigma Plot) after normality and homogeneity tests.