Brushite (CaHPO4·2H2O) to octacalcium phosphate (Ca8(HPO4)2(PO4)4·5H2O) transformation in DMEM solutions at 36.5 °C

The purpose of this study was to investigate the transformation of brushite (dicalcium phosphate dihydrate, DCPD, CaHPO4·2H2O) powders at 36.5 °C in DMEM (Dulbeccoʹs Modified Eagle Medium) solutions. Two sets of brushite powders with different particle shapes were synthesized to use in the above DMEM study. The first of these brushite powders was prepared by using a method which consisted of stirring calcite (CaCO3) powders in a solution of ammonium dihydrogen phosphate (NH4H2PO4) from 6 to 60 min at room temperature. These powders were found to consist of dumbbells of water lily-shaped crystals. The second one of the brushite powders had the common flat-plate morphology. Both powders were separately tested in DMEM-immersion experiments. Monetite (DCPA, CaHPO4) powders were synthesized with a unique water lily morphology by heating the water lily-shaped brushite crystals at 200 °C for 2 h. Brushite powders were found to transform into octacalcium phosphate (OCP, Ca8(HPO4)2(PO4)4·5H2O) upon soaking in DMEM (Dulbeccoʹs Modified Eagle Medium) solutions at 36.5 °C over a period of 24 h to 1 week. Brushite powders were known to transform into apatite when immersed in synthetic (simulated) body fluid (SBF) solutions. This study found that DMEM solutions are able to convert brushite into OCP, instead of apatite.