Vetorização termoinduzida de nanopartículas magnéticas biocompatíveis: uma aplicação no recobrimento de Stents nus por via líquida
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2011-08-23
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Universidade Federal de Goiás
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In this work we developed a Dip Coating method that could control the temperature gradient between a substrate and the material that one wants to adsorb at its surface. In particular, the adsorption of biocompatible magnetic nanoparticles at the surface of bare metal Stents, under different experimental conditions, was investigated. The magnetic nanoparticles consisted of magnetite coated with tripoliphosphate (mean diameter 7.68 nm and standard deviation 1.88 nm) dispersed in water at physiological conditions, while the Stent was a CoCr based-one (Cronus stent from Scitech with 16 mm length). Nine series of experiments were performed where it was controlled parameters as: time of adsorption, stent temperature and magnetic fluid temperature. The stents coated with nanoparticles were magnetically characterized using a vibrating sample magnetometer (VSM), which allowed us to determine the number of nanoparticles at the stent surface. The increase of the magnetic moment of the stent with the increase of the adsorption time was theoretically modeled, with an excellent experimental agreement, as a transient diffusion process of nanoparticles at the interface stent-magnetic fluid, which clearly indicates an important diffusive contribution. Strong evidences of thermal diffusion (Soret effect), i.e. nanoparticle diffusion due to temperature gradient between the stent and the magnetic fluid, were shown, suggesting the possibility of nanostructures vectorization through thermal induced mechanisms. The spatial distribution of nanoparticles at the surface of the stent was investigated by Scanning Electron Microscopy (SEM) and X-ray Spectroscopy by Dispersive Energy (EDS). Measurements of the compositional mapping and images of SEM revealed that the nanoparticles are not homogeneously distributed, being concentrated at the edges of the stents for the experimental conditions investigated in this work. As the VSM data, the EDS of the stents revealed an increase of the quantity of adsorbed magnetic nanoparticles at the surface with the increase of the adsorption time. The same theoretical model, know considering the amount of 26Fe in the chemical composition of the coated stent, was able to explain the experimental data. Finally, a comparison was made, using the compositional mapping study of the coated stents, between the Dip Coating and the Spray technique. The later showed a more homogeneous distribution of nanoparticles at the surface of the stent, suggesting that this technique is more adequate on the development of a biomedical nanoproduct for clinical tests.
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RODRIGUES, Harley Fernandes. Thermally induced vectorization of Biocompatible Magnetic Nanoparticles: an application to cover Bare Metal Stents by Dip Coating. 2011. 153 f. Dissertação (Mestrado em Ciências Exatas e da Terra) - Universidade Federal de Goiás, Goiânia, 2011.