Crystallization of calcium carbonates in biologically inspired collagenous matrices

Oriented crystallization of calcite, aragonite and vaterite by means of cross-linked collagenous matrices with entrapped poly-L-aspartate (poly-Asp) or poly-L-glutamate (poly-Glu) is reported. These results suggest that the control of calcium carbonate polymorphism and the architectural assembly of the crystals are related to the modelling of the nucleation sites in terms of polypeptide concentration, local supersaturation and shape. Orientation effect of the calcite has bean observed only with entrapped poly-Asp, indicating that the control over the oriented crystallisation is due to the beta structure assumed by the poly-Asp in the presence of calcium ions. The orientation of aragonite and vaterite can be controlled by the uniaxial deformation of the substrate. These results indicate that the local supersaturation in the microenvironment where nucleation and growth occur plays an important role in controlling the deposition of crystalline calcium carbonate polymorphs inside cross-linked gelatin films and that a structured organic scaffold can organize the crystalline units in unusual habitus. (C) 2000 Elsevier Science Ltd. All rights reserved.