Bioactivity and mechanical properties of polydimethylsiloxane (PDMS)-CaO-SiO2 hybrids with different PDMS contents

Much attention has been focused on the development of a new type of bioactive material with mechanical properties analogous to those of the natural bones. It has been reported that some polydimethylsiloxane (PDMS)-CaO-SiO2-TiO2 hybrids prepared by hydrolysis and polycondensation of PDMS, tetraethoxysilane (TEOS), tetraisopropyltitanate and calcium nitrate tetrahydrate show both apatite-forming ability in a simulated body fluid (SBF) and mechanical properties analogous to those of the human cancellous bones. PDMS-CaO-SiO2-TiO2 hybrids, however, released an appreciable amount of silicon into SBF, and the released amount of silicon increased with increasing TiO2 content in the examined composition. They might be unstable in body environment. In the present study, TiO2-free PDMS-CaO-SiO2 hybrids with different PDMS contents were synthesized by the sol-gel method, and their apatite-forming ability in SBF, silicon release into SBF and mechanical properties were investigated. The hybrid with PDMS/(TEOS + PDMS) weight ratio of 0.3, Ca(NO3)(2)/TEOS molar ratio of 0.15 and H2O/TEOS molar ratio of 2 showed high apatite-forming ability in SBF, little release of silicon into SBF as well as mechanical properties analogous to those of the human cancellous bones. This hybrid is expected to be useful as a new kind of bioactive material.