1. School of Materials Science and Engineering, Zhejiang University, Zheda Road 38, Hangzhou 310027, Zhejiang, P. R. China
2. Institute of Applied Bioresource Research, College of Animal Science, Zhejiang University, Yuhangtang Road 866, Hangzhou 310058, China
3. Department of Periodontology, The Second Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, 310009, P. R. China
4. Department of Chemistry & Biochemistry, Stephenson Life Science Research Center, Institute for Biomedical Engineering Science and Technology, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019-5251, USA