RESUMO
Layered double hydroxides (LDH) containing (Mg and Al) or (Zn and Fe) were prepared by coprecipitation at constant pH, using NaOH and urea as precipitation agents. The most pure LDH phase in the Zn/Fe system was obtained with urea and in Mg/Al system when using NaOH. The incorporation of phenyl-alanine (Phe) anions in the interlayer of the LDH was performed by direct coprecipitation, ionic exchange and structure reconstruction of the mixed oxide obtained by the calcination of the coprecipitated product at 400°C. The reconstruction method and the direct coprecipitation in a medium containing Phe in the initial mixture were less successful in terms of high yields of organic-mineral composite than the ionic exchange method. A spectacular change in sample morphology and yield in exchanged solid was noticed for the Zn3Fe sample obtained by ionic exchange for 6h with Phe solution. A delivery test in PBS of pH=7.4 showed the release of the Phe in several steps up to 25 h indicating different host-guest interactions between the Phe and the LDH matrix. This behavior makes the preparation useful to obtain late delivery drugs, by the incorporation of the anion inside the LDH layer.
Assuntos
Alumínio/química , Hidróxidos/química , Ferro/química , Magnésio/química , Zinco/química , Ânions/química , Cloretos/química , Compostos Férricos/química , Concentração de Íons de Hidrogênio , Nitratos/química , Fenilalanina/química , Hidróxido de Sódio/química , Espectroscopia de Infravermelho com Transformada de Fourier , Ureia/química , Compostos de Zinco/químicaRESUMO
In the present study, captopril-loaded ordered mesoporous SBA-15 silica matrix were produced, functionalized, and characterized to obtain an efficient formulation of controlled drug delivery system. First, the starting SBA-15 materials are examined to verify that their synthesis has been successful considering the structural properties, using XRD, FTIR, and BET methods. Second, the influence of processing parameters of ordered mesoporous matrices for the loading and release of captopril was investigated. The release of captopril was controlled by tailoring the surface properties of the mesoporous silica via functionalization. The loading and release kinetics (in vitro in simulated gastric and intestinal fluids) showed that both of them were affected by the surface properties of the mesoporous silica materials. Such a formulation shows potential as an efficient controlled drug delivery system.
Assuntos
Inibidores da Enzima Conversora de Angiotensina/administração & dosagem , Captopril/administração & dosagem , Preparações de Ação Retardada/química , Dióxido de Silício/química , Porosidade , Difração de Pó , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios XRESUMO
In this study we report the synthesis of a series of composite nanostructures comprising LDH and TiO2 phases. The materials characterization showed that the LDH crystallites are encapsulated inside the TiO2 matrix after the anatase seeds are deposited on MgxAl-LDHs. The structure in which LDH phase is embedded into anatase matrix is unique bringing important advantages to the photocatalytic performances of the nanocomposites. The photocatalytic activity of the prepared nanocomposites was tested on the degradation of the methylene blue (MB) in aqueous solution. The photocatalytic activities of the nanocomposites were compared with commercial TiO2 nanoparticles Degussa P25. The nanocomposites exhibited superior photocatalytic activity in basic environment because the negatively charged surface of TiO2 nanoparticles at high pH attracts the positively charged methylene blue species.
