Surface characterization and osteoblast-like Cells culture on collagen modified PLDLA scaffolds

Surface modification techniques based on the grafting of chemical functional groups and immobilization of bioactive molecules have been used to improve biocompatibility and clinical performance of bioabsorbable scaffolds in tissue engineering and medicine regenerative applications. This study aimed at developing and characterizing a biomimetic surface to stimulate bone regeneration by a simple and low-cost method of surface biofunctionalization of the poly (L-co-D,L lactic acid)- PLDLA scaffolds. The method was obtained by grafting reaction of carboxyl groups (-COOH) on their surface via acrylic acid (AAc) polymerization process, followed by immobilization of collagen type I (Col). Such approach resulted in a surface morphology markedly modified after treatment, with increase of pores and roughness on PLDLA-AAc surfaces and a network of fibrillar collagen deposition in nonspecific areas of PLDLA-Col surfaces. The cytocompatibility of collagen-immobilized scaffolds was significantly improved in terms of cellular adhesion, proliferation, collagen synthesis and maintenance of osteoblast-like phenotype, indicating, therefore, the fundamental role of collagen protein over the biological interactions that occur by bio-recognition mimetic mechanisms at biomaterials interface. These results indicate that the surface modification method used here may be useful as a strategy to develop biofunctional scaffolds, which provide a more successful clinical application of biomaterials in the tissue engineering field17615231534FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP2012/12081-2; 2007/05089-

Adsorção e ordenamento moleculares sobre paládio (111) : um estudo por HREELS e LEED

Orientador: Sandra Graça Carnicero de CastroTese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb WataghinResumo: Monocamadas de oxigênio coadsorvido com acetileno e etileno em uma superfície de Pd(111) foram estudadas por Espectroscopia de Alta Resolução por Perdas Energéticas de Elétrons ( "High Resolution Electron Energy Loss Spectroscopy" -HREELS) e Difração de Elétrons de Baixa Energia ("Low Energy Electron Diffraction" -LEED) a temperaturas de 150 a 320 K. A adsorsão de ambos C2H2 e C2H4 a baixa temperatura resultou em moléculas quimissorvidas não dissociativamente e a pré-adsorsão de oxigênio não modificou os resultados de LEED e HREELS.À temperatura ambiente ambos C2H2 e C2H4 formaram etilidino (C2H3), que se ordena fracamente na estrutura (Ö3xÖ3)R 30°. Descobri que a pré-adsorção de oxigênio induziu melhor ordenamento do C2H3 formado a partir da exposição de acetileno, mas não do C2H3 derivado da adsorsão de etileno. A sobrecamada de O + C2H3 sobre Pd(111) é o primeiro caso observado de ordenamento de um adsorvido orgânico induzido pela coadsorsão de oxigênio. É proposto que o oxigênio pré-adsorvido ajudou no ordenamento da sobrecamada de C2H3 por meio de: (a) remoção eficiente do hidrogênio superficial e (b) interação atrativa com C2H3 resultando em ordenamento induzido de coadsorvidosAbstract: Overlayers of oxygen coadsorbed with acetylene and ethylene on a Pd(111) surface have been studied by High Resolution Electron Energy Loss Spectroscopy (HREELS) and Low Energy Electron Diffraction (LEED) in the temperature range of 150 to 320 K. Low temperature adsorption of both C2H2 and C2H4 resulted in non-dissociatively chemisorbed molecules, and the pre-adsorption of oxygen did not change the LEED and HREELS data. At room temperature both C2H2 and C2H4 formed ethylidyne (C2H3), which poorly ordered in a(Ö3xÖ3)R 30° structure. It was found that pre-adsorption of oxygen induced better ordering for C2H3 formed from acetylene exposure, but not for C2H3 derived from ethylene adsorption. The O + C2H3 overlayer on Pd(111) is the first observed case of oxygen induced ordering of an organic adsorbate. It is proposed that pre-adsorbed oxygen helped the ordering of the C2H3 overlayer by (a) efficiently removing surface hydrogen and (b) attractively interacting with C2H3 to yield coadsorbate induced orderingDoutoradoFísicaDoutor em Ciência

Estudo de ligas catalíticas de paládio e ouro através de espectroscopia de fotoelétrons

Orientador: Sandra Graça Carnicero de CastroDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb WataghinResumo: Neste trabalho desenvolvemos o estudo sistemático de urna série de ligas PdxAu1-x, variando de Pd puro (x = 1) até Au puro (x = 0). A análise desse sistema por ESCA tem como objetivo obter informações sobre mudanças na estrutura eletrônica de Pd e Au quando da formação da liga. Medindo a variação da energia cinética da linha Au Auger MNN, chegamos à diferença entre os níveis de Fermi de Pd e Au, valor esse que concorda com resultado obtido através de medidas independentes. Corrigindo-se os deslocamentos de energia de ligação dos níveis internos medidos, levando em conta as mudanças de nível de Fermi, chega-se a conclusão que há desprezível transferência de recarga entre os componentes da ligaAbstract: We develop a systematic study of a series of PdxAu1-x alloys going from pure Pd (x = 1) to pure gold (x = 0). The analysis by ESCA gives information regarding changes in the electronic structure of Pd and Au upon the formation of the alloy. We measured the Au Auger kinetic energy shift and, through it, obtained the Fermi levels displacement between Pd and Au. This result agrees with the ones derived from two other sets of independent measurements. Correcting the core levels binding energy shifts by taking into account the Fermi level changes, we arrive at the conclusion of neglegible charge transfer between the alloy componentsMestradoFísicaMestre em Físic

Characterization of plasma nitrided layers produced on sintered iron

Plasma nitriding is a thermo-physical-chemical treatment process, which promotes surface hardening, caused by interstitial diffusion of atomic nitrogen into metallic alloys. In this work, this process was employed in the surface modification of a sintered ferrous alloy. Scanning electron microscopy (SEM), X-ray diffraction (XRD) analyses, and wear and microhardness tests were performed on the samples submitted to ferrox treatment and plasma nitriding carried out under different conditions of time and temperature. The results showed that the nitride layer thickness is higher for all nitrided samples than for ferrox treated samples, and this layer thickness increases with nitriding time and temperature, and temperature is a more significant variable. The XRD analysis showed that the nitrided layer, for all samples, near the surface consists in a mixture of γ′-Fe4N and ɛ-Fe3N phases. Both wear resistance and microhardness increase with nitriding time and temperature, and temperature influences both the characteristics the most

Materials Research

p. 431-436,Oct/Dec.The corrosion properties of a 22.5 wt. (%) Cr duplex stainless steel were investigated after long-term aging of 3000, 5000 and 7000 hours at 300 and 400 ºC. The corrosion resistance was measured based on mass loss in a FeCl3 10 wt. (%) solution and electrochemical measurements in a 0.1 M H2SO4 solution. The results indicate that the corrosion resistance decreased steadily up to 5000 hours of aging. However, the samples subjected to 7000 hours of aging showed better corrosion resistance than those aged for 3000 and 5000 hours. This effect is attributed to the phase transformation that occurs during aging, a finding which was confirmed by hardness, transmission electron microscopy and X-ray photoelectron spectroscopy measurements.São Paul

Effect of thermal aging conditions on the corrosion properties and hardness of a duplex stainless steel

The corrosion properties of a 22.5 wt. (%) Cr duplex stainless steel were investigated after long-term aging of 3000, 5000 and 7000 hours at 300 and 400 ºC. The corrosion resistance was measured based on mass loss in a FeCl3 10 wt. (%) solution and electrochemical measurements in a 0.1 M H2SO4 solution. The results indicate that the corrosion resistance decreased steadily up to 5000 hours of aging. However, the samples subjected to 7000 hours of aging showed better corrosion resistance than those aged for 3000 and 5000 hours. This effect is attributed to the phase transformation that occurs during aging, a finding which was confirmed by hardness, transmission electron microscopy and X-ray photoelectron spectroscopy measurements