WHAT HAVE WE LEARNED FROM MAS NMR ON BIOMATERIAL INTERFACES: EXAMPLES FROM BONE-LIKE APATITE

In recent years we have investigated the functionality of the peptides and proteins that are responsible for formation of materials in mammals and other living organisms. We analyzed both the impact on the biomaterials formed and the interface between these biomolecules and bioinspired materials that are prepared jointly. We utilize MAS NMR experiments to provide with intimate, often atomic, view of the effect of these tiny bioengineers on the biomineral formed complementing EM, TGA, ICP, XRD measurements.

In particular, the formation of the hard inorganic part of bone, depends on the functionality of the bone proteins such as osteocalcin, osteopontin and osteonectin. We found that the most recent model of bone mineral as being made of apatite crystallites, covered by layers of disordered calcium phosphate, needs to be revised to include an interphase which serves to relieve the inherent discontinuity of the model. We observed that bone proteins have a disparate effect on the mineral formed, osteonectin increases the disordered coat while osteocalcin minimizes it, the former operating within the disordered phase while the other in the interphase. Similar to the effect on the mineral, osteocalcin, crudely shows a better defined structure in complex with apatite than osteonectin.