Calcitic biomineralization and matrix proteins

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The protein components of biominerals (matrix proteins) influence the shape and strength of the final structure by modulating crystal nucleation and growth, which in turn defines the textural properties and crystal shape that strongly affect mechanical performance. However, the specific mechanisms through which this regulation is exercised remain unclear. My research program utilizes a novel model system to investigate how proteins influence calcification. The avian eggshell is one of the fastest calcifying processes known; 6 g of mineral is deposited in less than 20 hr during the daily formation of the chicken egg. This calcitic bioceramic is formed in the acellular uterine fluid, a milieu in which the ionic and protein composition varies during the initiation, rapid calcification and termination phases of mineral deposition. The integrity of this process is vital for the propagation of all avian species, since the eggshell is a physical and microbial barrier against the external environment in addition to regulating diffusion of water and metabolic gases, and providing a source of calcium to the growing embryo. Flaws in eggshell fabrication become a food safety issue, and are believed to be responsible for about 10,000 cases of salmonella poisoning due to cracked eggshells annually in Canada. The objectives of this application are to support research that will provide insight into how eggshell matrix proteins regulate calcite crystallization patterns.Significance: Food safety is an important aspect of the chicken eggshell, and these studies will lead to important understanding of how to enhance consumer protection by reducing eggshell cracks. In addition, the eggshell and its associated membrane is an important biomaterial resource that will have further utility in material science once its constituents and mechanism of fabrication are understood. Furthermore, insight into the mechanisms by which calcium carbonate precipitation and crystal growth patterns are regulated in this rapidly calcifying system will be useful for the manufacture of ceramics at ambient temperatures.