Bone composite behaviour: effects of mineral-organic bonding

Abstract

The mechanical properties of a composite material rely not only on the volume fraction, orientation and properties of the individual constituents, but upon their bonding interactions as well. This study examines the role of bonding between the mineral and organic constituents of bovine compact bone. Intact and completely demineralized samples were tested in tension following treatment in varying ionic strength sodium chloride or phosphate ion containing buffers to examine the interfacial bonding forces between bone's constituents. Phosphate ion treatment caused a reduction in the mechanical properties of intact samples but not in the demineralized samples. A sodium chloride solution with ionic strength equal to that of the phosphate ion buffer did not alter the mechanical properties of the intact or demineralized samples. Ash weight analysis, calcium probe measurements and SDS-gel electrophoresis indicated intact samples were not demineralized nor were bone structural proteins removed during treatment. Data suggest that the reduction in the mechanical properties of intact samples with phosphate ion treatment was due to an alteration in the interfacial bonding between the mineral and organic constituents of bone. Phosphate ions can compete with the negative domains of organic constituents for calcium binding sites of bone mineral and thereby interrupt or partially debond the interactions between the mineral and organic constituents of bone.