Hidroxiapatita mesoporosa pura e modificada organicamente com grupos nitrogenados síntese, caracterização e uso como carreadora de fármacos

• Autor(a) principal: Silva, Oberto Grangeiro da
• Data de Publicação: 2010
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFPB
• Texto Completo: https://repositorio.ufpb.br/jspui/handle/tede/7036
• topic: Sólidos mesoporosos; Hidroxiapatita; Liberação Controlada de Fármacos; Mesoporous solids; Hydroxyapatite; Controlled Drug Release; CIENCIAS EXATAS E DA TERRA::QUIMICA

Mesoporous materials present a highly ordered porous arrangement with narrow pore size distribution and high specific surface area, which are interesting features for adsorption and release of bioactive molecules. Another important feature of these solids is the presence of free hydroxyl groups on the pore walls that can react with functional organic moieties. Mesoporous solids have been synthesized by using specific molecules as templates which had to controlled polymerization in reactions. Thus, the present thesis describes the synthesis of mesoporous hydroxyapatite by using casein as a novel template. The mesoporous solids were functionalized with 3-aminepropyl-, 3-propylethylenediamine-, 3-propyldiethylenetriaminetrimethoxysilanes. The precursor and the modified phosphates derived from the silanization reactions were characterized by N2 adsorption, elemental analysis, X-ray diffraction, infrared spectroscopy, solid state 31P and 13C NMR, thermogravimetry and scanning electron microscopy (SEM). Both regular and mesoporous hydroxyapatites were studied on their ability to uptake and release bobine soroalbumine (BSA) from aqueous solutions. BSA was chosem as model guest compound. The nitrogen adsorption isotherms showed that structural aspects of the mesoporous hydroxyapatite are controlled by tuning experimental parameters, such as the calcination temperature, surfactant concentration, and pH. These isotherms also showed that casein is a promising biotemplate for synthesizing mesoporous calcium phosphates with improved values of specific surface area, such as 106 m2 g-1, which are higher than those found in the literature for analogous materials. Additionally, the template extraction was carried out during the washing process with water only, which avoided the need of spending time and energy with the calcinations step, and confirmed casein as an excellent template/surfactant in the synthesis of mesostructured materials. The BSA release kinetics decreased considerably as the silane amount increased on the silica surface. The organofunctionalized solids showed a lower BSA release rate, which decreased as the organic length chain increased. Thus, the amount of the organic groups, which contains nitrogen basic centers and interacts with BSA, controls the release process. The isotherms for releasing BSA showed a two step profile, with a fast release at the beginning, followed by a slower release rate, which fit the diffusion model proposed by Higuchi.