Osteoblast-like cell responses to silicate ions released from 45S5-type bioactive glass and siloxane-doped vaterite

Silicate ions released from bioactive glasses and ceramics have been reported to stimulate osteogenic cell functions. Here, we evaluated osteoblast-like cell reactions to silicate ions released from two different types of materials, 45S5 bioactive glass (BG) and siloxane-doped vaterite (SiV), to investigate the influence of the ionic structure of silicate ions on osteoblast-like cell properties. BG and SiV powders were prepared by using melt-quenching and carbonation methods, respectively. Aminopropyltriethoxysilane was used as a siloxane source of SiV. MC3T3-E1 and SaOS-2 cells were cultured in media containing dissolved BG or SiV ions (10–50 ppm of Si). Cell proliferation (metabolic activity), differentiation (alkaline phosphatase activity) and mineralisation (Ca deposition) were examined. ²⁹Si NMR spectra demonstrated that Q^0,1 species and T^0–3 species were released from BG and SiV, respectively. Proliferation and mineralisation of the two types of cells were influenced by silicate ions released from BG and SiV in a concentration-dependent manner. In particular, there were significant differences (P < 0.05) in the degree of proliferation and Ca deposition levels in SaOS-2 cells treated with dissolved BG and SiV ions. Furthermore, Ca deposition in SaOS-2 cells was influenced by both the presence of silicate ions and the duration of exposure of cells to them. The structure of silicate ions influenced the proliferation and mineralisation of SaOS-2 cells incubated for different time periods in culture media containing different Si concentrations. Understanding the effect of Si on bone cell behaviour will enable a design-led approach to further BG optimisation.