Counterintuitive Crystallization: Rate Effects in Calcium Phosphate Nucleation at Near-Physiological pH

Abstract

Calcium phosphates are widely present in geological and industrial settings and make up the majority of our bone's inorganic content; however, their formation from solution is not fully understood. The nucleation of calcium phosphate phases was studied using a state-of-the-art titration setup. The effect of varied calcium addition rate was studied at a range of pH values between pH 7 and pH 8; the precipitated crystals were isolated and analyzed. Dicalcium phosphate dihydrate (DCPD) was formed at lower pH and a slow addition rate. Intermediate addition rates yielded a mix of DCPD and poorly crystalline hydroxyapatite (PC-HA). At fast addition rates and above pH 7.5, poorly crystalline hydroxyapatite was precipitated exclusively. The results indicate that counterintuitive kinetic effects play a substantial role in the nucleation of calcium phosphates.

Mineralization of Octacalcium Phosphate under Magnetic Field

“…The HRTEM images of the ribbon particles showed a lattice stripe spacing of 0.81 nm and 0.34 nm (Figure S3), corresponding to (010) and (002) crystal planes, confirming the orientation of the ribbon OCP. The striped particles obtained after magnetic field treatment have more diffraction spots and higher crystallinity [27][28][29][30].…”