1. WPI-Advanced Institute for Materials Research; Tohoku University; Sendai 980-8577 Japan
2. Department of Chemistry and Division of Biomedical Engineering; Hong Kong University of Science and Technology; Hong Kong China
3. Institute of Multidisciplinary Research for Advanced Materials; Tohoku University; Katahira, Aoba-ku Sendai 980-8577 Japan
4. Department of Bioindustrial Technologies; College of Animal Bioscience and Technology; Konkuk University; Hwayang-dong, Kwangjin-gu Seoul 143-701 Republic of Korea
5. Biomaterials Innovation Research Center; Department of Medicine; Brigham and Women's Hospital; Harvard Medical School; Cambridge MA 02139 USA
6. Harvard-MIT Division of Health Sciences and Technology; Massachusetts Institute of Technology; Cambridge MA 02139 USA
7. Wyss Institute for Biologically Inspired Engineering; Harvard University; Boston MA 02115 USA. Department of Physics; King Abdulaziz University; Jeddah 21569 Saudi Arabia