Biomineralization of calcium phosphate revealed by in situ liquid-phase electron microscopy

Calcium phosphate biomineralization is essential to the formation of bones and teeth, and other pathological calcifications. Unravelling the mechanism of calcium phosphate nucleation and growth contributes significantly to understanding diseases caused by pathological mineralization, and also to designing biomimetic materials with suitable properties. Recently, calcium phosphate was proposed to mineralize following a non-classical crystal growth pathway of pre-nucleation cluster aggregation. Liquid-phase transmission electron microscopy allows dynamic processes to be recorded continuously inside liquid. Here we present direct evidence, based on continuous monitoring in liquid, to confirm that calcium phosphate mineralization from simulated body fluid occurs by particle attachment, shown with nanoscale spatial resolution and sufficient temporal resolution. This work may lay the foundation for future investigation of mineralization in other relevant biological systems in humans and vertebrates.