1. Department of Chemical and Biomolecular Engineering; National University of Singapore; 4 Engineering Drive 4 Singapore 117585 Singapore
2. The State Key Laboratory of Pharmaceutical Biotechnology; College of Life Science; Nanjing University; Nanjing 210023 China
3. Department of Biological Science; National University of Singapore; 14 Science Drive 4 Singapore 117543 Singapore
4. Department of Physiology; Yong Loo Lin School of Medicine; National University of Singapore; 2 Medical Drive Singapore 117597 Singapore
5. Institute of Materials Research and Engineering; 2 Fusionopolis Way Singapore 138634 Singapore