Spatiotemporal Regulation of Hierarchical Assembly of Hydroxyapatite for Enamel Remineralization

The hierarchical structure of tooth enamel confers exceptional mechanical robustness, yet its biomimetic regeneration remains a significant challenge. We develop an enzymatic mineralization system (EMS) that achieves enamel regeneration by directing the hierarchical assembly of hydroxyapatite (HAP). Within the EMS, the alkaline phosphatase hydrolyzes β-glycerophosphate (β-GP), triggering the mineralization reaction of calcium phosphate (CaP) and controlling its structural evolution. The mineralization process is characterized by a series of spatiotemporal events, in which CaP prenucleation clusters initially form and transform into HAP nanorod building blocks; these units then hierarchically self-assemble into microscale crystalline bundles that resemble native enamel rods. Mechanistically, differential adsorption of β-GP on the (100) and (002) facets of HAP, together with facet-dependent enzymatic cleavage of surface-bound β-GP, generates high-energy facets and interfacial energy differences that drive the hierarchical assembly, beginning with c-axis-oriented attachment followed by lateral aggregation. Extending this new strategy to enamel remineralization, the EMS restores the native microstructure and essential mechanical properties. Moreover, a hydrogel-based EMS demonstrates clinical translatability through effective in vivo repair. This paradigm of interfacial energy-modulated assembly provides a robust blueprint for the bottom-up construction of complex, high-performance biomimetic materials.