Fibrillar collagen is an important biological template, that provides nucleation sites for calcium phosphate crystals to form bones and teeth. During collagen mineralization, nucleation occurs at both nanoscale (intrafibrillar mineralization) and microscale (extrafibrillar mineralization). Unlike microscale nucleation, nucleation at nanoscale occurs in the highly confined gap regions of collagen. However, the thermodynamic aspects of these two mineralizations have not been fully evaluated due to the complexity of collagen’s fibrillar structure and the lack of in situ analytical tools. In this study, we separately determined the energy barriers for intra- and extrafibrillar mineralization by utilizing a modified version of classical nucleation theory that considers the plate-like morphology of bioapatite crystals. To quantify nucleation rates at different supersaturation of calcium phosphate minerals in the simulated body fluid, we used in situ X-ray scattering techniques. In the presence of polyaspartic acid as a nucleation inhibitor in the extrafibrillar space, nucleation dominantly occurs in the confined collagen gap regions. In these spaces where plate-like nuclei form, the active surface area for nucleation is limited, which decreases the surface energy and thus lowers the total nucleation energy barrier. Our findings provide a new explanation for how the highly confined spaces of collagen fibrils stimulate biomineralization.

Thermodynamics of confined calcium phosphate nucleation in collagen fibrils

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.