Biochemical approaches to investigate biomineralization of magnesium calcite and aragonite

Abstract

Biominerals are composites containing a very low percentage of organic matrix amidst a dense mineral phase. Despite having low organic contents, these natural materials are superior to most other synthetic composite ceramics in mechanical strength and toughness. Since biominerals are synthesized at ambient conditions without the need for the use of extremes of temperatures or pressures, understanding their mode of formation may help design novel hybrid materials with interesting properties. CaCO3 is one of the most common inorganic minerals produced by biological systems for constructing hard tissues and exists as three anhydrous polymorphs, namely, the calcite, aragonite and vaterite. Of these, marine organisms generally employ either calcite (usually with small amounts of magnesium ions replacing Ca2+ ions in the lattice) or aragonite form of the mineral. This thesis is focused on understanding the formation of such skeletons using biochemical methods. Representative members from the phyla echinodermata and mollusca have been chosen for investigations on the ultrastructure of the skeletal materials, analyzing the intramineral organic constituents using conventional biochemical techniques and understanding the role of the occluded biomacromolecules in mineralization. Mechanisms of formation of these skeletons have been proposed based on in vitro CaCO3 precipitation experiments conducted in the presence of proteins or glycosaminoglycans isolated from the ossicles/ shells under study.