Infiltration of Silica Inside Fibrillar Collagen

摘要

Diatom frustules (the hard and porous cell wall of diatoms) are created under the control of biomolecules (silaffins, silacidins, and long-chain polyamines) at close to physiologic conditions. The mechanism of biosilica formation was traditionally based on the ability of zwitterionic water-soluble proteins to create macromolecular assemblies for silica polymerization. Recent discoveries of water-insoluble collagen matrices within certain sponge biosilica spicules, chitin-based scaffolds in sponge and diatom biosilica formations, as well as cingulins within diatom girdle bands, revive the use of insoluble biomimetic organic templates for morphogenesis of nonporous silica structures. The use of fibrillar collagen as templates for biosilica synthesis was unsuccessful in the past as only extrafibrillar silica deposition was observed. Intrafibrillar mineralization of collagen has important implications from a biophysical perspective. Herein, we report a collagen biosilicification scheme based on the fusion of stabilized polysilicic acid into a fluidic precursor phase upon their infiltration into polyamine-enriched collagen. The latter serves as a template and catalyst for polymerization of the precursor phase into silica that faithfully reproduces the collagen tertiary architecture. Our findings provide a new concept in biosilica materials synthesis, which does not require phosphate supplements.