1. a Tissue Modulation Laboratory, National University of Singapore Tissue Engineering Programme, National University of Singapore, 117510 Singapore; Division of Bioengineering, Faculty of Engineering, National University of Singapore, 117576 Singapore; Immunology Programme, Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, 117456 Singapore
2. b Devro Plc, Glasgow G69 0JE, UK
3. c School of Applied Sciences, The University of Northampton, Northampton NN2 7AL, UK