1. Agency for Science, Technology and Research (A*STAR), Institute of Materials Research and Engineering (IMRE), 2 Fusionopolis Way, Singapore 138 634, Singapore
2. Agency for Science, Technology and Research (A*STAR), Institute of Molecular and Cell Biology (IMCB), 61 Biopolis Drive, Singapore 138 673, Singapore
3. Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, 1E Kent Ridge Road, NUHS Tower Block Level 7, Singapore 119 228, Singapore
4. Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Singapore