1. School of Chemistry Chemical Engineering and Biotechnology Nanyang Technological University 70 Nanyang Drive Singapore 637457 Singapore
2. Lee Kong Chian School of Medicine Nanyang Technological University 59 Nanyang Drive Singapore 636921 Singapore
3. National Engineering Research Centre for Nanomedicine College of Life Science and Technology Hubei Key Laboratory of Bioinorganic Chemistry and Materia Medical Huazhong University of Science and Technology 1037 Luoyu Road Wuhan 430074 P.R. China