Calcium carbonate nucleation driven by ion binding in a biomimetic matrix revealed by in situ electron microscopy

• Published in: Nature materials 2015-04, Vol.14 (4), p.394-399
• Main Authors: Smeets, Paul J. M., Cho, Kang Rae, Kempen, Ralph G. E., Sommerdijk, Nico A. J. M., De Yoreo, James J.
• Format: Article
• Language: English
• Subjects: 639/301/54/991; Binding; Biomaterials; Biomimetic Materials - chemistry; Biomimetics; Biomineralization; Calcium carbonate; Calcium Carbonate - chemistry; Condensed Matter Physics; Crystallization; Dissolution; Electron microscopy; Globules; Ions - chemistry; letter; Macromolecular Substances - chemistry; Macromolecular Substances - ultrastructure; Macromolecules; Materials Science; Materials Testing; Microscopy, Atomic Force; Microscopy, Electron, Transmission; Mineralization; Minerals - chemistry; Molecular Structure; Nanoparticles - chemistry; Nanoparticles - ultrastructure; Nanotechnology; Nucleation; Optical and Electronic Materials; Polymers; Polystyrenes - chemistry; Solutions
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/nmat4193

In situ liquid-phase electron microscopy experiments show that the binding of calcium ions to a biomimetic polymer matrix can direct the nucleation of amorphous calcium carbonate, a main precursor phase in calcium carbonate mineralization. The characteristic shapes, structures and properties of biominerals arise from their interplay with a macromolecular matrix 1 , 2 . The developing mineral interacts with acidic macromolecules, which are either dissolved in the crystallization medium or associated with insoluble matrix polymers 3 , that affect growth habits and phase selection or completely inhibit precipitation in solution 4 , 5 , 6 . Yet little is known about the role of matrix-immobilized acidic macromolecules in directing mineralization. Here, by using in situ liquid-phase electron microscopy to visualize the nucleation and growth of CaCO 3 in a matrix of polystyrene sulphonate (PSS), we show that the binding of calcium ions to form Ca–PSS globules is a key step in the formation of metastable amorphous calcium carbonate (ACC), an important precursor phase in many biomineralization systems 7 . Our findings demonstrate that ion binding can play a significant role in directing nucleation, independently of any control over the free-energy barrier to nucleation.