Potential of amorphous microporous silica for ibuprofen controlled release.

Amorphous microporous silica (AMS) xerogel materials were synthesized in an acid-catalyzed sol-gel process. The porosity of AMS was adapted by varying sol-gel synthesis parameters including the molar hydrolysis ratio (r-value), HCl:Si molar ratio, the type of silicon alkoxide source and the solvent. AMS particles of millimeter size were loaded with ibuprofen, by heat treatment and melt impregnation. In vitro release experiments were performed in simulated gastric and intestinal fluid. The release kinetics were critically depending on the AMS particle size distribution and the micropore diameter. The release was interpreted as configurational diffusion in the AMS micropores. The stability of unloaded and ibuprofen loaded AMS material upon storage was investigated using nitrogen physisorption, DSC analysis and in vitro release experiments. Ibuprofen loaded AMS formulations show remarkable stability, which can be attributed to the presence of ibuprofen molecules in the channels, functioning as scaffolds to support the pore structure.