Model Investigations of Controlled Release of Bioactive Compounds from Thin Metal Oxide Layers

Thin composite layers of silica with incorporated bioactive organic compounds (BOC) can be prepared by mixing metal oxide sols with dissolved BOC and coating with a conventional film coating machine. The release of antibacterial benzoic acid from the silica layers into a surrounding aqueous medium can be controlled by the mass ratio of silica to benzoic acid, by modification of the silica matrix and by addition of soluble or swelling penetration agents, respectively. Therefore, such composite materials are applicable for controlled release sytems in medicine and biology with excellent long-time effects.