1. Ming Wai Lau Centre for Reparative Medicine, Karolinska Institutet, Hong Kong, P. R. China.
2. School of Science, Harbin Institute of Technology, Shenzhen, HIT Campus of University Town, Shenzhen 518055, P. R. China.
3. Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, P. R. China.