MC3T3-E1 proliferation and differentiation on biphasic mixtures of Mg substituted β-tricalcium phosphate and amorphous calcium phosphate

Abstract

A low temperature aqueous approach was used to synthesize nanocrystalline, high surface area Mg2+ substituted β-tricalcium phosphate (β-TCMP) to assess its potential use as a synthetic bone graft substitute. X-ray diffraction indicated that β-TCMP was the predominant crystalline phase formed. However, thermal analysis revealed the presence of a secondary amorphous phase which increased with increasing Mg2+ concentration. Further analysis by Rietveld refinement indicated that the level of ionic substitution of Ca2+ by Mg2+ was significantly lower than the amount of Mg2+ measured using elemental analysis, confirming the formation of a Mg2+ rich secondary amorphous phase. MC3T3-E1 proliferation on substrates prepared using β-TCMP was assessed using the MTT assay. In comparison to commercially available β-TCP, increased proliferation was observed on samples prepared with 50% Mg, despite elevated Mg2+ and PO43− concentrations in culture media. Alkaline phosphatase (ALP) activity and qRT-PCR were used to study the effect of varying Mg2+ substitution on osteogenic differentiation. Cells cultured on β-TCMP substrates prepared with increased Mg2+ concentrations expressed significantly increased levels of ALP activity and osteogenic genes such as, osteocalcin, collagen-1, and Runx2, in comparison to those cultured on commercially available β-TCP.