Synthesis of sol–gel silica materials providing a slow release of biphosphonate

The aim of this study was to synthesize silica materials that would provide a slow release of biphosphonate. The biphosphonate used in this work, etidronate, is a small water-soluble molecule that can be used to inhibit bone resorption in the body, since calcium ions can be complexed to the biphosphonate through a bidentate bond. This kind of silica material could therefore serve as active filler in polymer-based implants. The biphosphonate was incorporated into the silica during the spray-drying step, and the silica could provide a slow release on the month time-scale. The release process is suggested to be controlled by both erosion and diffusion processes.