The Avian Eggshell as a Model of Biomineralization
- PDF / 4,959,770 Bytes
- 9 Pages / 420.48 x 639 pts Page_size
- 36 Downloads / 169 Views
THE AVIAN EGGSHELL AS A MODEL OF BIOMINERALIZATION JOSE L. ARIAS*, MARIA S. FERNANDEZ*, VINCENT J. LARAIA, JAROSLAW JANICKI, ARTHUR H. HEUER and ARNOLD I. CAPLAN Skeletal Research Center, Departments of Biology and Material Sciences and Engineering, Case Western Reserve University, Cleveland, Ohio 44106 *Visiting Scientists from University of Chile, Santiago ABSTRACT The avian eggshell is one of the most rapidly mineralizing biological systems known. By understandi'ng the key components and steps in this process, we hope to provide relevant information for fabrication of ceramic composites. The calcification of the eggshell occurs in three main steps: 1) fabrication of an organic matrix, 2) nucleation of an inorganic phase on the organic matrix, and 3) space-filling growth of the calcite phase. The different layers of an eggshell can be separately isolated and studied. Three approaches have been used in our study of the eggshell: 1) characterization of the organization and chemical composition of the shell, 2) selective removal or blocking of particular components to improve the remineralization of demineralized shells, and 3) addition of new components to produce composite ceramics of different kinds. In this preliminary communication, the organization of the shell matrix and membranes and their association with the crystal phase, the immunohistochemical occurrence and distribution of types I and X collagen, and of different proteoglycans are reviewed. Also the preliminary findings of the remineralization of the intact or modified eggshell are presented. These experiments allow us to identify the essential steps in forming a natural composite ceramic. INTRODUCTION Biological hard tissues including bones, teeth and shells are fabricated by living cells by combining an organic fibrillar network or scaffold, referred to as the extracellular matrix, with a crystalline inorganic filler. These natural or biological composite ceramics are fabricated at relatively low temperatures of 10-40*C, and do not involve the high temperatures required to fabricate man-made ceramics. The principles governing the natural fabrication process may provide the basis for mimicking these biological events in controlled conditions to create new, lowtemperature, man-made ceramic composites. To accomplish this goal, we need first to understand the basic mechanisms and details of structure, synthesis and the control of the assembly of natural model systems, in this case the avian eggshell. The avian eggshell is one of the most rapidly mineralizing biological systems known: 5 g of calcium carbonate are crystallized in the less than 20 hrs required to fabricate the shell in situ I I ]. This massive mineralization (or crystal deposition) combined with an apparent relative simplicity, provides a useful model for the study of the process of biomineralization. The calcification of the eggshell occurs in three main steps: 1) fabrication of an organic matrix (shell membranes and Mat. Res. Soc. Symp. Proc. Vol. 218. @1991 Materials Research Society
1
Data Loading...
