Biomimetic mineralization of calcium carbonate mediated by a polypeptide-based copolymer

A novel copolymer, beta-cyclodextrin-b-poly(L-glutamic acid) (beta-CD-b-PLGA), was synthesized by ring-opening polymerization and subsequent hydrolysis reaction. The beta-CD-b-PLGA copolymer possesses an oligosaccharide beta-CD segment and a polypeptide PLGA segment, with chemical structure resembling natural glycoprotein. The copolymers were applied in regulating the crystallization of calcium carbonate. The effects of the concentration of copolymers and calcium ions were systemically investigated. Various morphologies, including rhombohedra, rod, pseudo-dodecahedra and rosette-like structures, were obtained by adjusting the polymer and Ca2+ concentrations of the initial solution. Investigation of the pseudo-dodecahedra growth mechanism indicates that the copolymers mediate amorphous calcium carbonate formation initially, and then regulate the meso-scale self-assembly of CaCO3 subunits. The morphology variation is influenced by the binding of beta-CD-b-PLGA chains on specific crystal faces combined with the steric repulsive force of beta-CD-b-PLGA chains.