title: Control of Polymorph Selection in Amorphous Calcium Carbonate Crystallization by Poly(Aspartic Acid): Two Different Mechanisms.
abstract: Poly(aspartic acid) (pAsp) is known to stabilize amorphous calcium carbonate (ACC) and affect its crystallization pathways. However, little is known about the mechanisms behind these phenomena. Here it is shown that ACC is stabilized by pAsp molecules in the solution rather than by the amount of pAsp incorporated into the ACC bulk, and that the effect of pAsp on the polymorph selection is entirely different at low and high concentration of pAsp. At low concentrations, pAsp is more effective in inhibiting the nucleation and growth of vaterite than calcite. At high concentrations, when calcite formation is prevented, the crystallization of vaterite proceeds via a pseudomorphic transformation of ACC nanospheres, where vaterite nucleates on the surface of ACC nanospheres and grows by a local transformation of the bulk ACC phase. These results shed some light on the function of pAsp during an ACC-mediated biomineralization process and provide an explanation for the presence of metastable vaterite at conditions where calcite is thermodynamically favored.
authors.affiliation: Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Potsdam, 14424, Germany.
authors.forename: Zhaoyong
authors.initials: Z
authors.lastname: Zou
authors.affiliation: Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Potsdam, 14424, Germany.
authors.forename: Luca
authors.initials: L
authors.lastname: Bertinetti
authors.affiliation: Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Potsdam, 14424, Germany.
authors.forename: Yael
authors.initials: Y
authors.lastname: Politi
authors.affiliation: Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Potsdam, 14424, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Fratzl
authors.affiliation: Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Potsdam, 14424, Germany.
authors.forename: Wouter J E M
authors.initials: WJEM
authors.lastname: Habraken
keywords: amorphous; aspartic acid; calcium carbonate; nanospheres; pseudomorphic transformation