BONE COMPOSITE BEHAVIOR - EFFECTS OF MINERAL ORGANIC BONDING

The mechanical properties of a composite material rely not only on the volume fraction, orientation and properties of the individual constit uents, but upon their bonding interactions as well. This study examine s 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 interfaci al 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 ion ic strength equal to that of the phosphate ion buffer did not alter th e mechanical properties of the intact or demineralized samples. Ash we ight analysis, calcium probe measurements and SDS-gel electrophoresis indicated intact samples were not demineralized nor were bone structur al proteins removed during treatment. Data suggest that the reduction in the mechanical properties of intact samples with phosphate ion trea tment was due to an alteration in the interfacial bonding between the mineral and organic constituents of bone. Phosphate ions can compete w ith the negative domains of organic constituents for calcium binding s ites of bone mineral and thereby interrupt or partially debond the int eractions between the mineral and organic constituents of bone.