1. Department of Materials, Imperial College School of Science and Technology, Prince Consort Road, London SW1 2BP, UKTel.: , Fax:
2. Department of Histochemistry, Imperial College School of Medicine, The Hammersmith Hospital, Ducane Rd, London W12 ONN, UK
3. Centre for Tissue Engineering, Imperial College School of Medicine, Chelsea and Westminster Hospital, 369 Fulham Road, London SW10 9NH, UK