Collagen-fibril matrix properties modulate the kinetics of silica polycondensation to template and direct biomineralization

Abstract

Fibrillar collagen networks template and direct biocompatible silica mineralization to produce hybrid materials for biomedical applications. Silica mineralization kinetics is critical for precision-tuning material properties, including mechanical strength, microstructure, and interface thickness. We investigated the effect of varying collagen template fibril volume fraction (0.2-0.8) and elasticity (G′ 200-1500 Pa) on silica mineralization rates. Measurement of the depletion of mono- and disilicic acids by silicomolybdic acid titration showed that silica condensation on collagen fibrils follows third-order kinetics. Resulting third-order rate constants increased linearly with storage modulus and quadratically with fibril volume fraction. A unique rheological approach used to probe the collagen template surface elasticity in real-time during silicification suggested a two-phase mechanism with high levels of surface-localized gelation in Phase 1 and high levels of bulk solution-localized gelation in Phase 2. These results provide a tool for controlling hybrid collagen-silica material properties by controlling local silica condensation rates.