Síntese e caracterização de nanocompósitos de sílica mesoporosa com partículas magnéticas para dispositivos de liberação controlada de fármacos




Ordered mesoporous materials like SBA-15 posses a network of channels and pores of well-defined size in the nanoscale range. This particular pore architecture makes them suitable for hosting a broad variety of compounds into the silica matrix, resulting in very promising material for a broad range of applications, including magnetic carriers for drug delivery. In this work, magnetic nanocomposites embedded into mesoporous silica were prepared in two steps. Firstly, magnetite was synthesized by oxidation-precipitation method from a solution of iron sulfate, potassium nitrate and potassium hydroxide. After this, the magnetic nanoparticles were coated with mesoporous silica by using nonionic block copolymer surfactants as structure-directing agents. Characterization of the materials was carried out by using X-ray diffraction (XRD), 57Fe Mössbauer spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), N2 adsorption, energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), XRay Photoeletron Spectroscopy (XPS) and magnetic measures. Our results revealed a wellordered mesopore structure of the nanocomposite, suggesting that the samples structure can be described as a honeycomb of hexagonal mesopores separated by continuous silica walls and the coating layer is distributed over the magnetic nanoparticles. The average size of magnetite particles obtained by XRD data was about 38 nm. Mössbauer spectroscopy showed that magnetite is preserved in the applied synthesis route. Both XPS data and TEM had shown that the silica recovers magnetite particles, forming a composite with particle sizeof 138 nm. Finally, the influence of these magnetic particles in the release kinetic was studied using drugs like cisplatin, carboplatin and atenolol; this study was made under in vitro conditions. The release was studied in absence and presence of a external magnetic field, using a NdFeB permanent magnet of 0,25 T. The kinetic mechanisms and diffusion models were investigated by the external field, and the results had showed a small influence of this parameter on the process of drug release. Considering that nanoparticles are coated by mesoporous silica, this result is expected. Then, a test was made to verify the influence of an oscillating field in the release profile and the results showed a more significant delivery for cisplatin. To explain this fact, an interaction model between this drug and the nanocomposite was proposed.


silica, difração de raio x drugs materials materiais porosos materiais porous materials silica drogas composite materials x ray diffraction biomateriais e materiais biocompativeis

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