1. College of Animal Sciences Zhejiang University Hangzhou 310058 P. R. China
2. School of Biological & Chemical Engineering Zhejiang University of Science & Technology Hangzhou 310023 P. R. China
3. Zhejiang Engineering Research Center for Biomedical Materials Cixi Institute of Biomedical Engineering Ningbo Institute of Materials Technology and Engineering Chinese Academy of Sciences Ningbo 315300 China