Apatite Formation on PDMS-Modified SiO2-CaO-P2O5 Hybrids Prepared with Different P2O5 Content by Sol-Gel method

초록

Bioactive ORMOSILS (organically modified silicate), PDMS-CaO-SiO2-P2O5 with five different P2O5 content (0, 0.01, 0.03, 0.06, 0.09 mol%) were successfully synthesized by sol-gel process. The hybrids were prepared with polydimethylsiloxane (PDMS), tetraethoxysilane (TEOS), calcium nitrate tetrahydrate [Ca(NO3)2ㆍ4H2O] and triethyl phosphate (TEP) as starting materials and subsequently soaked into the simulated body fluid (SBF) with ionic concentrations nearly equal to those in human plasma for different period of time. The bioactivity of hybrids was determined by examining the apatite formation on the surface of the specimen by Fourier Transform Infrared Reflection Spectroscopy, Thin-Film X-ray Diffraction, Scanning Electron Microscopy (SEM) and X-ray Energy Dispersive Spectroscopy (EDS). All of the prepared samples with different P2O5 content showed in vitro bioactivity. It was observed that the increase in P2O5 content up to 0.03 mole % increases the apatite formation compared to P2O5-free hybrids. The induction period for the apatite formation decreased from 9 hours for the P2O5-free hybrid to 6 hrs for 0.03 mol% P2O5 hybrid. However, further increase in P2O5 concentration slows down the formation of the apatite layer most probably due to the decrease of pH of SBF by dissolution of a large amount of phosphate ions. Results obtained by SEM-EDS showed that the sample containing 0.03 mole% P2O5 resulted in the thickest apatite layer(~6μm) after 15 days in SBF.