Monolithic polydimethylsiloxane-modified silica composites prepared by a low-temperature sol-gel micromolding technique for controlled drug release

Sol-gel derived multi-component silica composites are widely accepted as smart materials in orthopedic surgery as bone fillers and bioactive skeleton drug delivery systems. This paper discusses the effect of hydroxy-terminated polydimethylsiloxane (PDMS) (10, 20, 30 and 40% (w/w)) on the physicochemical properties of low temperature sol-gel processed polydimethylsiloxane/calcium phosphate/silica (PDMS-modified CaP/SiO2) composites. The micromolding technique was employed to obtain PDMS-modified CaP/SiO2 composites-monolithic granule-type formulations. The effectiveness of PDMS-modified CaP/SiO2 granules as potential skeleton drug delivery systems was studied in vitro using Rhodamine B (ROD) as a model for highly water-soluble molecules. Results indicated that the composites with PDMS contents at 20 and 30% (w/w) showed similar mechanical properties to those of human cancellous bones. The content of PDMS had a significant effect on the release of ROD. These results showed that PDMS-modified CaP/SiO2 granules with 20 and 30% (w/w) PDMS could provide the zero-order release profile of highly water-soluble molecules.