1. Department of Biophysics, School of Basic Medical Sciences, Health Science Centre Xi'an Jiaotong University Shaanxi 710061 P. R. China
2. Department of Spine Surgery, Honghui Hospital Xi'an Jiaotong University Shaanxi 710061 P. R. China
3. Bioinspired Soft Matter Unit Okinawa Institute of Science and Technology Graduate University Okinawa 904-0495 Japan