Protein-assisted synthesis of double-shelled CaCO 3 microcapsules and their mineralization with heavy metal ions

Abstract

Calcium carbonate (CaCO 3) is one of the most abundant and important biominerals in nature. Due to its biocompatibility, biodegradability and nontoxicity, CaCO 3 has been investigated extensively in recent years for various fundamental properties and technological applications. Inspired by basic wall structures of cells, we report a protein-assisted approach to synthesize CaCO 3 into a double-shelled structural configuration. Due to varying reactivities of outer and inner shells, the CaCO 3 microcapsules exhibit different sorption capacities and various resultant structures toward different kinds of heavy metal ions, analogical to biologically controlled mineralization (BCM) processes. Surprisingly, three mineralization modes resembling those found in BCM were found with these bacterium-like "CaCO 3 cells". Our investigation of the cytotoxicity (MTT assay protocol) also indicates that the CaCO 3 microcapsules have almost no cytotoxicity against HepG2 cells, and they might be useful for future application of detoxifying heavy metal ions after further study. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.