Synthesis, characterisation and in vitro evaluation of sol–gel derived SiO2–P2O5–CaO–B2O3 bioactive system

Multicomponent xB2O3[100−x](61SiO2·9 P2O5·30CaO] system with 0≤x≤30 mol% was prepared by sol–gel method. The morphology of the 600 °C heat treated samples was characterised through Scanning Electron Microscopy (SEM). X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy and X-ray Photoelectron Spectroscopy (XPS) were used to characterise the local structure, the nature of the chemical bonding and the surface composition of these samples. Up to 10 mol% B2O3 the samples have a glass-ceramic character, a crystalline phase characteristic to hydroxyapatite being detected through XRD measurements. With further increasing x the samples present a vitreous character. FTIR spectroscopy revealed a complex silicate and phosphate network consisting mainly of meta- and pyro-type units. The development of hydroxyapatite, A and B-type of carbonate-substituted hydroxyapatite was followed based on FTIR and XPS spectra analysis. The bioactivity of the samples has been analysed in vitro in simulated body fluid (SBF). The evolution of apatite layers self-assembled on the samples surface after immersion in SBF was analysed and discussed as a function of both boron content and immersion time. The results indicate that after five days of immersion, the microstructure of the sample with 10 mol% B2O3 is quite close to that of dry human trabecular bone