Cephalexin adsorption onto SBA-15 mesoporous silica

M. SOLEDAD LEGNOVERDE; ELENA I. BASALDELLA; R. M. TORRES SANCHEZ

Simposio; 3rd International Symposium Advanced Micro and Mesoporous Materials; 2009

Cephalexin is an antibiotic of the group of the cephalosporins, â-lactam antibiotics. They are among the safest and the most effective broad-spectrum bactericidal antimicrobial agents [1]. As the average life time of cephalexin is about 0.9 hours, immobilization and stabilization in a matrix is required. Furthermore, mesoporous silica materials are recently proposed as new hosts for stabilizing different pharmaceuticals [2-4]. In particular, SBA-15 mesoporous silica could adsorb drugs of different sizes, since the pore diameter of the silica matrix can be tailored to the desired value, with the extra bonus of high specific surface and absence of microbial pathogens. These properties suggest that SBA-15 could be an excellent pharmaceutical excipient for drug adsorption and further controlled release. Besides, the chemical nature of the adsorbate surface can be modified by functionalization, altering matrix  adsorption-desorption properties. In this paper the loading capacity of cephalexin on SBA-15 was investigated using UV-VIS spectroscopy. In order to have a better knowledge about the way the drug molecules interact with the inorganic matrix, the drug-loaded silica was studied by N2 adsorption, SEM, thermal analysis and zeta potential determinations. Impregnation leads to a decrease in surface area and pore volume, indicating the drug adsorption inside the mesopores. SEM morphologies of SBA-15 with and without drug impregnation showed no changes. Zeta potential values obtained as a function of pH for the silica with and without drug impregnation showed modification of the surface charge due to the antibiotics adsorption. Loaded cephalexin showed a good stability, as observed by FTIR spectroscopy analysis. Desorption process is currently under study.