ACP-Mediated Phase Transformation for Collagen Mineralization: A New Understanding of the Mechanism.

Despite significant efforts utilizing advanced technologies, the contentious debate surrounding the intricate mechanism underlying collagen fibril mineralization, particularly with regard to amorphous precursor infiltration and phase transformation, persists. This work proposes an amorphous calcium phosphate (ACP)-mediated pathway for collagen fibril mineralization and utilizing stochastic optical reconstruction microscopy technology, and has experimentally confirmed for the first time that the ACP nanoparticles can infiltrate inside collagen fibrils. Subsequently, the ACP-mediated phase transformation occurs within collagen fibrils to form HAP crystallites, and significantly enhances the mechanical properties of the mineralized collagen fibrils compared to those achieved by the calcium phosphate ion (CPI)-mediated mineralization and resembles the natural counterpart. Furthermore, demineralized dentin can be effectively remineralized through ACP-mediated mineralization, leading to complete restoration of its mechanical properties. This work provides a new paradigm of collagen mineralization via particle-mediated phase transformation, deepens the understanding of the mechanism behind the mineralization of collagen fibrils, and offers a new strategy for hard tissue repair.