1. Research Institute of Polymer Materials, Tianjin University, Tianjin 300072, People's Republic of China, Department of Orthopaedics & Traumatology, Xijing Hospital, Xi'an 710032, The Fourth Military Medical University, People's Republic of China, Department of Orthopedic Surgery, National University of Singapore, Singapore 119260, Division of Bioengineering, National University of Singapore, Singapore 119260