Estudo das características físico-químicas e biológicas pela adesão de osteoblastos em superfícies de titânio modificadas pela nitretação em plasma

SILVA, J. S. P. Estudo das características físico-químicas e biológicas pela adesão de osteoblastos em superfícies de titânio modificadas pela nitretação em plasma. 2008. 119 f. Tese (Doutorado) - Faculdade de Medicina, Universidade de São Paulo. São Paulo, 2008.

Adesão, proliferação e genotoxicidade celular de celulose bacteriana modificada por plasma

Bacterial cellulose (BC) has a wide range of potential applications, namely as temporary substitute skin in the treatment of skin wounds, such as burns, ulcers and grafts. Surface properties determine the functional response of cells, an important factor for the successful development of biomaterials. This work evaluates the influence of bacterial cellulose surface treatment by plasma (BCP) on the cellular behavior and its genotoxicity potential. The modified surface was produced by plasma discharge in N2 and O2 atmosphere, and the roughness produced by ion bombardment characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Cell adhesion, viability and proliferation on BCP were analysed using crystal violet staining and the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium (MTT) method. Genotoxicity was evaluated using the comet and cytokinesis block micronucleus assay. The results show that the plasma treatment changed surface roughness, producing an ideal cell attachment, evidenced by more elongated cell morphology and improved proliferation. The excellent biocompatibility of BCP was confirmed by genotoxicity tests, which showed no significant DNA damage. The BCP has therefore great potential as a new artificial implant

Superfícies de titânio modificadas termoquimicamente por plasma : avaliação da resposta biológica

This laboratory study involves the participation of a group with professionals from different areas that had contributed to the construction of a multidisciplinary knowledge, about biological response of titanium surfaces modified through thermochemical treatment by plasma. Thus, the crystalline phase was previously characterized in relation to the topography, roughness, molhability and nitrogen concentration in the samples surface. It s indispensable that materials implanted can influence in a good cellular response as well as promotes a bacteria action. Surfaces modified by plasma were exposed to different cultures such as: cellular (human osteoblastic) and bacteria (Staphylococcus epidermidis ATCC35984 and Pseudomonas aeruginosa ATCC 27853) in order to evaluate the biological response. It was evaluated the adhesion, proliferation, morphology and cellular preference of human ostheoblastic cells (HOST), as well as the formation of a biofilm and bacteria proliferation. It was still analyzed the bacteria selectivity ability in relation to the surfaces. The software Image Pro Plus was used to the counting of cells and bacteria adhered to the surface of disks. The results were submitted to the variance analysis (ANOVA), and then, by the Kruskal-Wallis test, using GraphPad Instat ® software, version 3.5 to Windows. The nitrided samples in spite of show a higher roughness and molhability showed a smaller bacteria growing and higher cellular proliferation, when compared to non treated samples, indicating that the treated material present a high efficiency to biomedical implants

Conversor CC/CA de alta freqüência baseado em inversores ressonantes com comutação seqüencial para excitação de uma tocha indutiva a plasma térmico

This work describes the study, the analysis, the project methodology and the constructive details of a high frequency DC/AC resonant series converter using sequential commutation techniques for the excitation of an inductive coupled thermal plasma torch. The aim of this thesis is to show the new modulation technique potentialities and to present a technological option for the high-frequency electronic power converters development. The resonant converter operates at 50 kW output power under a 400 kHz frequency and it is constituted by inverter cells using ultra-fast IGBT devices. In order to minimize the turn-off losses, the inverter cells operates in a ZVS mode referred by a modified PLL loop that maintains this condition stable, despite the load variations. The sequential pulse gating command strategy used it allows to operate the IGBT devices on its maximum power limits using the derating and destressing current scheme, as well as it propitiates a frequency multiplication of the inverters set. The output converter is connected to a series resonant circuit constituted by the applicator ICTP torch, a compensation capacitor and an impedance matching RF transformer. At the final, are presented the experimental results and the many tests achieved in laboratory as form to validate the proposed new technique

Descarga em barreira dielétrica: construção de um reator DBD e caracterização mediante análises ópticas e elétricas do plasma produzido

The plasma produced by Dielectric Barrier Discharge (DBD) is a promising technique for producing plasma in atmospheric pressure and has been highlighted in several areas, especially in biomedical and textile industry, this is due to the fact that the plasma generated by DBD not reaches high temperatures, enabling use it for thermally sensitive materials. But still it is necessary the development of research related to understanding of the chemical, physical and biological interaction between the non-thermal plasma at atmospheric pressure with cells, tissues, organs and organisms. This work proposes to develop equipment DBD and characterize it in order to obtain a better understanding of the process parameters of plasma production and how it behaves under the parameters adopted in the process, such as distance, frequency and voltage applied between electrodes. For this purpose two techniques were used to characterize distinct from each other. The first was the method of Lissajous figures, this technique is quite effective and accurately for complete electrical characterization equipment DBD. The second technique used was Optical Emission Spectroscopy (EEO) very effective tool for the diagnosis of plasma with it being possible to identify the excited species present in the plasma produced. Finally comparing the data obtained by the two techniques was possible to identify a set of parameters that optimize the production when combined DBD plasma atmosphere in the equipment was built precisely in this condition 0.5mm-15kV 600Hz, giving way for further work

Estudo das características físico-químicas e biológicas pela adesão de osteoblastos em superfícies de titânio modificadas pela nitretação em plasma

SILVA, J. S. P. Estudo das características físico-químicas e biológicas pela adesão de osteoblastos em superfícies de titânio modificadas pela nitretação em plasma. 2008. 119 f. Tese (Doutorado) - Faculdade de Medicina, Universidade de São Paulo. São Paulo, 2008.