Eggshell Mineralization: A Case Study of a Bioprocessing Strategy
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Eggshell Mineralization: A Case Study of a Bioprocessing Strategy David J. Fink, Arnold I. Caplan, and Arthur H. Heuer In its composition, architecture, and function, the eggshell is an elegant solution Description: A package is required to conto the design problem posed above —a tain approximately 50 ml (55-60 grams) of a multilayered bioceramic composite, conviscous, 2-phase, thermally labile, aqueous sisting of a mineral phase (primarily calmedium containing proteins, carbohydrates, cite, CaCO3) deposited on and within a salts, nucleic acids and fats. A seamless ellip- complex organic phase (the matrix). The soidal container is anticipated having a eggshell provides a unique microenvironmaximum radial dimension of 45 mm and a ment for housing embryonic development. maximum axial dimension of 60 mm. The It protects the embryo, regulates respiracontainer wall must be permeable to respira- tory gases, water and ions, and provides tory gases and water vapor. External surface calcium for embryonic skeletal developtexture must be minimal. White coloration is ment. As such, the eggshell represents an acceptable, but the ability to incorporate solid example of widespread evolutionary strator patterned surface coloration is desirable. egy across many species, including those The package wall must weigh approximately with soft (uncaldfied) shells (snakes, most 5 g, the material must contain at least 0.3 g lizards), pliable calcareous (partially crysof bioavailable calcium, and it must be recy- talline) shells (most turtles, tuatara (unique clable and biodegradable. The container must New Zealand lizards)), and rigid calcarewithstand 400-g drop test impacts. ous (highly calcified) shells (crocodiles, birds, some turtles, geckos, and all identiProcessing: All materials must be mainfied dinosaurs).1 tained and the container fabricated by aseptic The basic features of eggshell structure processing in neutral-pH, aqueous medium were identified by von Nathusius and others at less than 40°C and with a unit production in the mid-19th century.2 While it is now time of less than 24 hours. possible to describe the structure of the eggUnit cost: Filled unit containers must be shell in some detail—including its crystal produced for approximately $4.00/100 units, habit and texture, and the composition of with approximately $1.00/100 units allocated its primary organic constituents—the preto container components and assembly. cise fabrication mechanism of this structure is still only poorly understood; further Laboratory Solution: Not achievable in the research will be required before we reach laboratory. the point of mimicking this system for advanced mineralized materials. Biological Solution: The eggshell. Product Concept: Fluid packaging device.
MRS BULLETIN/OCTOBER 1992
This paper summarizes the known properties of the composite structure of the eggshell of the domestic hen. A working hypothesis for the steps and control systems governing eggshell assembly are then deduced from an analysis of the known structural features and com
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