1. Institute of Pharmaceutics; College of Pharmaceutical Sciences; Zhejiang University; Hangzhou Zhejiang 310058 P. R. China
2. Dr. Li Dak Sum & Yip Yio Chin Center for Stem Cell and Regenerative Medicine; Zhejiang University; Hangzhou Zhejiang 310058 P. R. China
3. Center for Bionanoengineering and Key Laboratory of Biomass Chemical Engineering of Ministry of Education; College of Chemical and Biological Engineering; Zhejiang University; Hangzhou Zhejiang 310027 P. R. China
4. Department of Radiology; Sir Run Run Shaw Hospital; School of Medicine; Zhejiang University; Hangzhou Zhejiang 310016 P. R. China
5. Institute of Materials Science and Engineering; A*STAR; Singapore 138634 Singapore
6. Department of Regeneration Science and Engineering; Institute for Frontier Life and Medical Sciences; Kyoto University; Kyoto 606-8501 Japan