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Site Directed Nucleation and Growth of Ceramic Films on Metallic Surfaces

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Final rept. 15 Feb 206-31 Jan 2009

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Phylum Mollusca produce a variety of calcium carbonate shells. Recent research efforts have focused on elucidating the actual mechanism of shell formation the advent of molecular biology has facilitated identification of specific proteins and genes involved in crystal and shell formation. As a result of this funded effort, much progress has been made towards understanding the involvement of cellular biomineralization by hemocytes refractive granulocytes, or REF cells in the Eastern oyster Crassostrea virginica. We have devised a mineralization model which includes spatial and temporal control of hemocyte-mediated crystal nucleation and crystal growth on an underlying organic matrix. We have confirmed circulating immune blood cells hemocytes are directly involved in oyster shell formation, where two mineralized layers of shell prismatic and foliated are deposited in conjunction with an organic polymer matrix. The key steps in layered shell formation that have been determined are 1 secretion of an organic matrix film for cells to adhere 2 migration of cells onto this membrane to form a mineralization front 3 deposition of nanocrystals of intracellular origin by specialized cells 4 formation of polycrystalline assemblies within cellular agglomerations 5 epithelial directed growth of polycrystalline assemblies to form a uniform mineralized layer 6 subsequent secretion of second organic matrix film onto the mineralized layer. These results challenge the prevailing shell formation paradigm which holds that shell components calcium carbonate and organic matrix are secreted in a complex milieu and that assembly into calcium carbonate aragonite and calcite shell layers is matrix-media. The paradigm shift is this initiation and control of molluscan biomineralization is a cellular process.

Subject Categories:

  • Biology
  • Inorganic Chemistry
  • Crystallography

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