Micro-PIXE–RBS methods highlighting the influence of phosphorus on the in vitro bioactivity of sol–gel derived glass particles in the SiO2–CaO–P2O5 system

Ion beam analysis methods were used to characterize the interface of bioactive glasses with surrounding biological fluids. Glass particles in the SiO2–CaO and SiO2–CaO–P2O5 compositions were made by sol–gel processing and soaked in biological fluids for periods up to 4 days. The surface changes were characterized using PIXE–RBS, which are efficient methods for multielemental analysis and accurate trace elements quantification. Elemental maps of major and trace elements were obtained at a micrometer scale and revealed the bone bonding ability of the materials. Glass particles are quickly coated with a thin calcium phosphate-rich layer containing traces of magnesium. After a few days, SiO2–CaO–P2O5 glass particles are entirely changed into calcium phosphates, whereas SiO2–CaO particles exhibit a different behavior: the previously Ca–P enriched periphery has been dissolved and glass particles consist of a silicate network. Calculation of the Ca–P atomic ratios at the glass/biological fluids interface provides us with an explanation for this: an enduring apatitic phase seems to be formed at the periphery of SiO2–CaO–P2O5 glass particles. Presence of phosphorus in the glass matrix thus has an influence on the amplitude and the kinetics of reaction of the bioactivity process. It might result in an improved chemical bond with living tissues.