Preparation of bioactive flexible poly(tetramethylene oxide) (PTMO)–CaO–Ta2O5 hybrids

Poly(tetramethylene oxide) (PTMO)–CaO–Ta2O5 hybrids were prepared by hydrolysis and polycondensation of triethoxysilane-functionalized PTMO (Si–PTMO), tantalum ethoxide (Ta(OEt)5) and CaCl2. In the system CaO-free PTMO–Ta2O5, Si–PTMO/Ta(OEt)5 weight ratios were 30/70, 40/60 and 50/50 (hybrids PT30Ca0, PT40Ca0 and PT50Ca0, respectively). In the system PTMO–CaO–Ta2O5, the Si–PTMO/Ta(OEt)5 weight ratio was 40/60 and CaCl2/Ta(OEt)5 mole ratios were 0.05, 0.10 and 0.15 (hybrids PT40Ca5, PT40Ca10 and PT40Ca15, respectively). Crack-free transparent monolithic hybrids were obtained for all the examined compositions except for PT30Ca0. Even CaO-free hybrids PT40Ca0 and PT50Ca0 formed apatite on their surfaces in a simulated body fluid (SBF) within 14 days. Hybrid PT40Ca0 showed higher mechanical strength, which was increased by soaking in SBF, and larger strain to failure than human cancellous bone. The CaO-containing hybrids showed higher apatite-forming ability than the CaO-free hybrids, and its apatite-forming ability increased with increasing CaO content. Hybrids PT40Ca10 and PT40Ca15 formed apatite within 3 days. The mechanical strength of PT40Ca15 was, however, lower than PT40Ca0 and was decreased by soaking in SBF. Thus obtained flexible bioactive CaO-free PTMO–Ta2O5 hybrids are expected to be useful as bone substitutes.