Insights into structural characteristics and the mechanism of silicate-based calcium phosphates with phosphoric acid modulation

Si-containing calcium phosphate materials recently have attracted attention owning to their biomineral capability and benefit to the proliferation and differentiation of osteoblast-like cells. In this study, tri-calcium silicate (C3S), which can induce apatite layer deposition on its surface, and phosphoric acid are used to prepare silicate-based calcium phosphates via aqueous precipitation method. It's known that calcium phosphate undergoes phase transformation when the pH value changes. So, the different ratios of C3S and phosphoric acid are designed to study the phase transformation of calcium phosphate. The pH, ions release of solution, composition and structure are detected. The results show the phase transformation of calcium phosphate from hydroxyapatite to brushite with the increased content of phosphoric acid. The structure of calcium silicate hydrate (C-S-H) also undergoes a series of changes, including protonation and polymerization. Briefly, this study focuses primarily on the interaction between C-S-H and calcium phosphates. In addition, it may provide a new sight for the sustained delivery of bisphosphonates achieved by depositing on the surface of C3S for the treatment of osteoporosis.