1. College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610065, P. R. China
2. Experimental and Research Animal Institute, Sichuan University, Chengdu 610065, P. R. China
3. State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, P. R. China
4. Med-X Center for Materials, Sichuan University, Chengdu 610041, P. R. China