The formulation of a bioresponsive ceramic bone replacement

The long-term stability and brittle nature of ceramic bone replacements in physiological conditions makes them prone to mechanical failure. These problems have led to the development of bioresorbable bone replacement materials. Bioresorbable biomaterials are expected to degrade at a rate which is proportional to the rate of formation of new bone tissue. In the majority of cases, however, resorption is driven by simple dissolution and so it is difficult to ensure an appropriate degradation rate for all patients. This thesis seeks to develop a material that can degrade in response to the bone formation process, thus linking implant resorption to tissue formation. We have shown that this can be achieved by linking implant resorption to a biological stimulus, such as the enzyme alkaline phosphatase (ALP), which is found on the surface of bone forming cells (osteoblasts). ALP causes bone mineralisation by removing the pyrophosphate (P₂O₇^4-) ion, a known inhibitor to calcium phosphate formation. By removing the P₂O₇^4- P2O74- ions from solution the dissolution of calcium pyrophosphate ((Ca₂P₂O₇^4-) crystals were accelerated in accordance with Le Chetalier's principle. We demonstrated that for this accelerated dissolution to occur, the ALP did not require access to the crystal surface. This is contrary to previous work which suggested that CPPD dissolution occurred as a result of ALP cleaving the crystal surface. Bulk (Ca₂P₂O₇\ ceramics were successfully produced by sintering brushite cement at temperatures ≥ 400°C, the dissolution of which could accelerated in the presence of ALP but was heavily dependent on material specific surface area. The process of sintering limits the possibility of producing biomaterials of complex morphology; therefore the final part of this thesis involved the fabrication of ((Ca₂P₂O₇ ceramic using stereolithography.

Name dc:type.qualificationname

d_ph

Level dc:type.qualificationlevel

d_ph

Grantor dc:publisher.institution

University of Birmingham

Year dc:date.issued

2010

Author dc:creator

• Bolarinwa, Aminat

• TP Chemical technology