Periodic nucleation of calcium phosphate in a stirred biocatalytic reaction

Abstract

Highly ordered superstructures composed of inorganic nanoparticles appear in natural and synthetic systems, however the mechanisms of non-equilibrium self-organization that may be involved are still poorly understood. Herein, we performed a kinetic investigation of the precipitation of calcium phosphate using a process widely found in microorganisms: the hydrolysis of urea by enzyme urease. With high initial ratio of calcium ion to phosphate, periodic precipitation was obtained accompanied by pH oscillations in a well-stirred, closed reactor. We propose that an internal pH-regulated change in the concentration of phosphate ion is the driving force for periodicity. A simple model involving the biocatalytic reaction network coupled with burst nucleation of nanoparticles above a critical supersaturation reproduced key features of the experiments. These findings may provide insight to the self-organization of nanoparticles in biomineralization and improve design strategies of biomaterials for medical applications.

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Identifiers

ORCID for Tamás Bánsági: orcid.org/0009-0000-0279-2353

ORCID for Annette F. Taylor: orcid.org/0000-0003-0071-8306

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