Crystallization of calcium carbonates in biologically inspired collagenousmatrices

Oriented crystallization of calcite, aragonite and vaterite by means of cro ss-linked collagenous matrices with entrapped poly-L-aspartate (poly-Asp) o r poly-L-glutamate (poly-Glu) is reported. These results suggest that the c ontrol 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, indic ating 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 ori entation of aragonite and vaterite can be controlled by the uniaxial deform ation of the substrate. These results indicate that the local supersaturati on in the microenvironment where nucleation and growth occur plays an impor tant role in controlling the deposition of crystalline calcium carbonate po lymorphs inside cross-linked gelatin films and that a structured organic sc affold can organize the crystalline units in unusual habitus. (C) 2000 Else vier Science Ltd. All rights reserved.