Controlled synthesis of plate-shaped hydroxyapatite and implications for the morphology of the apatite phase in bone.

A general methodology for predicting the conditions for the formation of plate-shaped structures by precipitation has been developed. The method has been applied for understanding the morphology of hydroxyapatite formed under different synthetic conditions. Morphology diagram has been developed in the form of pH-T diagrams to predict regions where plate-shaped hydroxyapatite is expected to form. The validity of the morphology diagram has been tested by critical experiments carried out at different conditions coupled with detailed microstructural analysis. Different morphologies ranging from single crystalline sheets, rods to equiaxed particles of hydroxyapatite are achieved by tuning the driving force of the precipitation reactions by varying the parameters such as pH and temperature in the absence of capping/surfactant agents. The synthesis and analysis presented here have important implications for understanding the plate-shaped morphology of apatite crystals that exist in the bone.