Cambridge Centre for Medical Materials

History

Current group members

Group photograph

Past group photographs

Group alumni & their research

Social

Professor William Bonfield CBE FRS FREng BSc(Eng) Imperial College 1958 PhD Imperial College 1961 Fellow of The Royal Academy of Engineering 1993 CBE 1998 Fellow of The Royal Society 2003

Biomaterials are either modified natural or synthetic materials which find application in a spectrum of medical implants for the repair, augmentation and replacement of body tissues. One well known example is the total replacement of an arthritic joint by an artificial prosthesis based on appropriate biocompatible engineering materials.

While providing an effective solution for many patients, the outcome is often time limited. As a consequence, our research is focussed on the innovation of second generation biomaterials derived from the biological template, and in tissue engineering, with the potential for enhanced, or even an infinite, lifetime in the patient.

Substituted calcium phosphates for skeletal implants
Hydroxyapatite, Ca₁₀(PO₄)₆(OH)₂, which resembles bone mineral, has achieved significant application as a bone graft in a range of medical and dental applications. Recent work has demonstrated that specific ion substitution in phase pure hydroxyapatite can produce an enhanced rate of integration into a skeletal site, with important implications for cementless fixation of implants and prostheses. The effects of controlled substitution of carbonate, silicate, sodium, magnesium, and fluoride ions into phase pure hydroxyapatite, alone and in combination, are being investigated in a systematic programme, with associated determination of structural, mechanical and biological performance.

Bioactive composites as bone analogues
A bone analogue, based on a tailor made hydroxyapatite reinforced polyethylene composite (HAPEX™), has achieved clinical success as a middle ear prosthesis and is a prime example of progressing a second generation biomaterial from laboratory concept to major applications in patients. The innovation of a range of derivative composites for specific medical and dental applications is in progress, with appropriate mechanical and biological properties. Candidate bioactive components include substituted hydroxyapatite, and A-W glass ceramic, in association with stable and degradable polymeric matrices.

Tissue engineering
The prospects for bone tissue engineering are being considered, through the incorporation of specific cell types and proteins into various, controlled porosity, polymer and ceramic matrices. Particular emphasis is being given to the processes leading to cell attachment and the expression of extra cellular matrix, as well as to the innovation of combined cartilage-bone substitutes.

References
D. VASHISHTH, J.C. BEHIRI, W. BONFIELD, "Crack growth resistance in cortical bone: concept of microcrack toughening", Journal of Biomechanics, 30 (8), 763-769 (1997).

W. BONFIELD, M. WANG, K.E. TANNER, "Interfaces in analogue biomaterials", Acta. Mater., 46 (7), 2509-2518 (1998).

F.J. GUILD, W. BONFIELD, "Predictive modelling of the mechanical properties and failure processes of hydroxyapatite-polyethylene (HAPEX™) composite", Journal of Materials Science: Materials in Medicine, 9 , 621-624 (1998).

I.R. GIBSON, S.M. BEST, W. BONFIELD, "Chemical characterisation of silicon-substituted hydroxyapatite", Journal of Biomedical Materials Research, 44, 422-428 (1999).

K.A. HING, S.M. BEST, K.E. TANNER, W. BONFIELD, P.A. REVELL, "Quantification of bone ingrowth within bone-derived porous hydroxyapatite implants of varying density", Journal of Materials Science: Materials in Medicine, 10, 663-670 (1999).

Professor Bonfield's biography