1. Department of Chemical Engineering, National University of Singapore, Kent Ridge, Singapore 119260, Republic of Singapore, Tissue & Therapeutic Engineering Lab, Level 5 Clinical Research Center, Johns Hopkins Singapore Biomedical Center, NUS, 10 Medical Drive, Singapore 117597, Republic of Singapore, Department of Chemistry, Wuhan University, Wuhan 430072, P. R. China, and Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205