Multistep Growth Mechanism of Calcium Phosphate in the Earliest Stage of Morphology-Controlled Biomineralization

Abstract

We studied the effect of surface-functional-group position on precipitate morphology in the earliest stage of calcium phosphate biomineralization and determined the detailed mechanism of precipitation starting from nucleation to precipitate growth. The biomineralization template was a β-sheet peptide scaffold prepared by adsorption with carboxyl groups arranged at strict 7 Å intervals. Phosphate was then introduced. Within 10 s, highly ordered embryos of calcium phosphate were formed and confined by a peptide nanofiber pattern. They repeatedly nucleated and dissolved, with the larger embryos absorbing the smaller ones in a clear demonstration of an Ostwald-ripening-like phenomenon, then aggregated in a line pattern, and finally formed highly ordered nanofibers of amorphous calcium phosphate. This multistep growth process constitutes the earliest stage of biomineralization.