Study on MgxSr3-x(PO4)2 bioceramics as potential bone grafts.

Magnesium (Mg) and strontium (Sr), which are essential nutrient elements in the natural bone, positively affect the osteogenic activity even in wide ranges of ion concentrations. However, it remains unknown whether magnesium-strontium phosphates [MgxSr3-x(PO4)2] are potential bone grafts for accelerating bone regeneration. Herein, a serial of MgxSr3-x(PO4)2, including Mg3(PO4)2, Mg2Sr(PO4)2, Mg1.5Sr1.5(PO4)2, MgSr2(PO4)2 and Sr3(PO4)2, were synthesized using a solid-state reaction approach. The physicochemical properties and cell behaviors of MgxSr3-x(PO4)2 bioceramics were characterized and compared with the common bone graft ß-tricalcium phosphate (ß-TCP). The results indicated that various MgxSr3-x(PO4)2 bioceramics differed in compressive strength and in vitro degradation rate. All the MgxSr3-x(PO4)2 bioceramics had excellent biocompatibility. In contrast to ß-TCP, the MgxSr3-x(PO4)2 enhanced alkaline phosphatase activity of mouse bone mesenchymal stem cells (mBMSCs), and inhibited osteoclastogenesis-related gene expression of RAW264.7 cells, but did not enhance osteogenesis-related gene expression of mBMSCs which were treated with osteogenesis induction supplements. However, Mg3(PO4)2 stimulated osteogenesis-related gene expression of mBMSCs without the treatment of osteogenesis induction supplements. This work contributes to the design of bone graft and may open a new avenue for the bone regeneration field.