1. National Engineering Laboratory for Modern Silk and Collaborative Innovation Center of Suzhou Nano Science and Technology Soochow University Suzhou 215123 P. R. China
2. School of Biology and Basic Medical Sciences Soochow University Suzhou 215123 P. R. China
3. Department of Orthopedics The First Affiliated Hospital of Xiamen University Xiamen 361000 P. R. China
4. Department of Biomedical Engineering Tufts University Medford MA 02155 USA