Incorporation of Ca2+ ions in gelatin-siloxane hybrids through a sol-gel process

Several gelatin-siloxane hybrids incorporating Ca2+ ions were synthesized t hrough a sol-gel process starting with gelatin, 3-(glycidoxypropyl) trimeth oxysilane (GPSM), and Ca(NO3)(2). Amino acid analysis, Si-29 NMR spectrosco py, Fourier-transform infrared (FT-IR) spectroscopy, and dynamic mechanical thermal analysis were used to assess the hybrid structure. It has been ind icated that the grafting degree of epoxy groups of GPSM to gelatin and the extent of polymerization of methoxysilane end groups of GPSM strongly depen ded on the fraction of GPSM (f(G)) in the hybrids, but not on incorporation of Ca2+ ions. Hence, the hybrids with the same f(G) value, independent of incorporation of Ca2+ ions, had a similar cross-link density. However, the glass transition temperature (T-g) and storage modulus (E') around T-g decr eased with incorporation of Ca2+ ions. Through the deconvolution of amide I bands of FT-IR spectra, flexibility may be interpreted by that the percent age of gelatin having a random structure increased with incorporation of Ca 2+ ions. The Ca2+-containing hybrids can spontaneously deposit apatite when they were soaked in a simulated body fluid of the Kokubo recipe, showing t heir bioactivity.