PNNL

Abstract

Enamel formation is regulated by interfacial interactions between the protein amelogenin with forming calcium phosphate phases at different stages of mineralization. This includes guiding the assembly of amorphous calcium phosphate precursors into needles that transform to hydroxyapatite (HAP) crystals. However, it is unclear how protein associates with the forming mineral phase due to long-standing challenges in resolving complex organic-inorganic interfacial structures. Here, three-dimensional atom probe tomography (3D APT) was utilized to directly visualize the nanoscale protein structure and to measure distributions across interfaces in an amelogenin-mineralized HAP system in vitro. Specifically, amelogenin was trapped between HAP nanometer-sized particles, indicating incorporation during particle aggregation and fusion can occur. Interpretations and analyses were further supported by systematic investigations using simple interfacial structures, i.e., amelogenin adsorbed onto a well-defined, (100) HAP surface. This work provides unprecedented insight into fundamental protein-mineral interactions, alluding to mechanisms influencing enamel formation and, more broadly, biomineralization.