Evidence for Epitaxy in the Formation of Collagen and Apatite

Abstract

A NUMBER of structural relationships between the organic and inorganic components of bone are known from X-ray diffraction and electron microscopy studies. The interrelationships have led to a theory of mineralization involving the process of epitaxy, that is, the orientated overgrowth of bone mineral on certain well crystallized areas of the organic matrix. This differs in principle from theories of mineralization which assign no active role to the organic matrix in the mineralization process. Epitaxy clearly requires some structural symmetry, but considerable mismatch seems to be permissible in the process of crystal seeding. Results reported here indicate a structural symmetry in collagen and apatite in the presence of copper ion and support the concept of epitaxial growth; areas of identical crystal order on apatite and the organic substrate have been demonstrated as would be expected if epitaxy were a relevant mechanism.