Amelogenin Promotes the Formation of Elongated Apatite Microstructures in a Controlled Crystallization System

The organic matrix in forming enamel consists largely of the amelogenin protein self-assembled into nanospheres that play a pivotal role in controlling the oriented and elongated growth of highly ordered apatitic crystals during enamel biomineralization. However, the mechanisms of amelogenin-mediated mineralization have not yet been fully elucidated. Here we report that amelogenin dramatically accelerates the nucleation kinetics by decreasing the induction time in a dose-dependent manner in a controlled constant composition (CC) in vitro crystallization system. Remarkably, at very low protein concentrations, elongated microstructures which are similar in appearance to apatitic crystals in enamel were formed at relatively low supersaturations, through interfacial structural match/synergy between structured amelogenin assemblies and apatite nanocrystallites. This heterogeneous crystallization study provides experimental evidence to support the concept that templating by amelogenin very early in the crystallization process facilitates the formation of developing enamel crystals.