Interfacial binding and mechanistic insights into enzyme-mediated homogeneous mineralization on TiO₂ nanotubes: A combined experimental and multi-scale computational study

Abstract

Enzyme-mediated mineralization offers a versatile strategy for developing advanced composite biomaterials, yet the precise mechanisms involving kinetic mineral-interface bonding and mineral growth remain elusive. Herein, we systematically optimized the parameters for alkaline phosphatase (ALP)-mediated mineralization on TiO₂ nanotubes (TNT) surfaces. To bridge the gap between macroscopic observations and microscopic origins, we employed an integrated approach combining molecular dynamics simulations (MDS) and first-principles calculations to elucidate the underlying atomistic and electronic-level mechanisms. Experimental results demonstrated that ALP regulates mineralization by catalyzing the hydrolysis of organic phosphate, thereby maintaining a sustained and controllable local supply of PO₄³⁻ ions. Molecular dynamics simulations revealed that ALP acts as a molecular regulator by forming stable ALP-CaP clusters. These clusters temporarily delay the direct aggregation of Ca²⁺ and PO₄³⁻ ions, therefore preventing premature precipitation and promoting homogeneous mineral deposition within the TNT scaffolds. Subsequently, first-principles calculations provided deep insights into the electronic structure, identifying specific coordination sites and quantifying the interfacial binding energies between these mineral precursors and the TNT internal surfaces. The analysis confirms that ALP residues bridge CaP clusters to the TNT interface via Ca²⁺–O_–COO– (coordination bond) and O_PO₄³⁻–H_–NH₂ (hydrogen bond), while Ca²⁺ ions from the clusters anchor simultaneously to the TNT. These multi-point interactions and charge redistribution collectively enhance the interfacial binding energy. The resulting composites exhibit a potent inductive effect on osteogenesis. This synergy of experiment and theory provides a comprehensive understanding of the interfacial physics driving mineral deposition during enzyme-mediated mineralization, laying the foundation for the development of functional biomimetic interfaces.

Keywords

Surface coordination / Interfacial binding energy / Enzyme-mediated homogeneous mineralization / Molecular dynamic simulation / First-principles study

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