High phosphate content in bioactive glasses promotes osteogenesis in vitro and in vivo

High phosphate content was found to significantly increase apatite formation of bioactive glasses (BGs) in vitro. However, there is very limited understanding of the effect of phosphate contents on osteogenesis which is important for clinical applications. The aims of this study were to investigate how phosphate content influences apatite formation ability of bioactive glasses in α-MEM culture medium and whether high phosphate content in bioactive glasses promotes osteogenesis in vitro and in vivo.

Four phosphate containing bioactive glasses were synthesized via a melt-quench method and characterized using X-ray powder Diffraction (XRD), TGA-DSC and Fourier transform infra-red spectroscopy (FTIR). The apatite formation ability in α-MEM culture medium and the in vitro and in vivo osteogenic potential of these bioactive glass were explored.

FTIR spectra confirmed faster apatite formation with an increase in phosphate content. The culture media containing ions released from the BGs showed enhanced cell viability and alkaline phosphatase activity of osteoblasts. Osteoblasts cultured with extracted BGs culture media generally showed increased proliferation, mineralized nodule formation, osteogenic and angiogenic genes expression with an increase in phosphate content in the glass compositions. An in vivo study demonstrated a larger amount of new bone formation in the calvarial defects implanted with high phosphate containing BG granules compared with that of BG without the presence of phosphate at 8 weeks post-surgery.

The presence of higher phosphate content accelerates apatite formation and promotes osteogenesis, indicating that both apatite formation and osteogenesis of bioactive glasses can be tailored by varying phosphate content for specific clinical needs and personalized treatments.