Accelerated transformation of brushite to octacalcium phosphate in new biomineralization media between 36.5 °C and 80 °C

This study investigated the hydrothermal transformation of brushite (dicalcium phosphate dihydrate, DCPD, CaHPO4·2H2O) into octacalcium phosphate (OCP, Ca8(HPO4)2(PO4)4·5H2O) in seven different newly developed biomineralization media, all inspired from the commercial DMEM solutions, over the temperature range of 36.5 °C to 90 °C with aging times varying between 1 h and 6 days. DCPD powders used in this study were synthesized in our laboratory by using a wet-chemical technique. DCPD was found to transform into OCP in the Ca2+, Mg2+, Na+, K+, HCO3−, Cl− and H2PO4− containing aqueous biomineralization media in less than 72 h at 36.5 °C, without stirring. The same medium was able to convert DCPD into OCP in about 2 h at 75–80 °C, again without a need for stirring. Samples were characterized by using powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM).

Research highlights
► New biomineralization solutions developed to convert DCPD into OCP at 36.5 °C to 80 °C.
► DCPD powder was the starting material.
► OCP was synthesized under static conditions (no need for stirring).
► OCP was synthesized in sealed glass media bottles in solutions free of Hepes or Tris.
► OCP can be synthesized at 75–80 °C in only 2 hours in the above solutions without stirring.