Biomimetic deposition of calcium phosphates on oxides soaked in a simulated body fluid

Abstract 31P magic-angle-spinning (MAS) NMR spectra were measured for several oxides, such as Al2O3, SiO2, TiO2 and Ta2O5 which were treated with TaCl5-free H2O2 solutions and TaCl5-containing H2O2 solutions and soaked in a simulated body fluid (Kokubo solution; pH=7.4) for 7 days. The chemical states of phosphate anions deposited on these oxides were determined. A 31P MAS-NMR peak at a chemical shift ca. 3 ppm was observed in the spectra of Ta2O5 and for the other oxides when they were treated with the TaCl5-containing H2O2 solution. Without the treatment with the TaCl5-containing H2O2 solution no 31P MAS-NMR peaks were observed in the spectra of the oxides. The 31P chemical shift, ca. 3 ppm, indicated that orthophosphate anions, PO43− as found in hydroxyapatite and a cortical bone (rabbit) were adsorbed on the oxides. The surface of Ta2O5 particles and the oxides treated with the TaCl5-containing H2O2 solution induced the deposition of apatite. We concluded that the surface Ta(V) species supported on the oxides induced a bone-like apatite nucleus, even though the base oxides did not deposit apatite.