Molecular Origin of the Biologically Accelerated Mineralization of Hydroxyapatite on Bacterial Cellulose for More Robust Nanocomposites

Biomineralization generates hierarchically structured minerals with vital biological functions in organisms. This strategy has been adopted to construct complex architectures to achieve similar functionalities, mostly under chemical environments mimicking biological components. The molecular origin of the biofacilitated mineralization process is elusive. Herein, we describe the mineralization of hydroxyapatite (HAp) accompanying the biological secretion of nanocellulose by Acetobacter xylinum. In comparison with mature cellulose, the newly biosynthesized cellulose molecules greatly accelerate the nucleation rate and facilitate the uniform distribution of HAp crystals, thereby generating composites with a higher Young modulus. Both simulations and experiments indicate that the biological metabolism condition allows the easier capture of calcium ions by the more abundant hydroxyl groups on the glucan chain before the formation of hydrogen bonding, for the subsequent growth of HAp crystals. Our work provides more insights into the biologically accelerated mineralization process and presents a different methodology for the generation of biomimetic nanocomposites.

Automated summary

Biomineralization in organisms generates hierarchically structured minerals with vital biological functions. The biological secretion of nanocellulose can greatly accelerate nucleation rate, facilitate uniform distribution of crystals, and create composites with higher Young modulus. The biological metabolism conditions allow easier capture of calcium ions for subsequent growth of crystals.