31P MAS-NMR studies of phosphate salts formation on calcium-containing oxide glasses in a simulated body fluid

31P MAS-NMR spectra were measured for pulverized binary and ternary glasses containing Ca2+ ions after soaking in a simulated body fluid (Kokubo solution; pH = 7.25) for 1 d, and the chemical state of adsorbed phosphate ions were examined. The 31P chemical shift indicated that orthophosphate ions, HxPO4-(3-x) (02O3; pyrophosphate ions, HzP2O7-(4-z) (02O3, 40CaO&middot60B2O3, 40CaO&middot30B2O3&middot30Al2O3 and 40CaO&middot30B2O3&middot30SiO2, those phosphate ions gave broad 31P MAS-NMR spectra, hence have a broad distribution by coordinating to the various surface sites of the glasses. On the other hand, sharp 31P MAS-NMR spectra as for a cortical bone (rabbit) were obtained for the rest of the glasses, 50CaO&middot50SiO2 and 40CaO&middot30B2O3&middot30TiO2, on which apatite formed in shorter soaking period in the Kokubo solution. It was thus concluded that presence of orthophosphate ions on the glass surfaces favored the deposition of apatite.