1. Institute of Hybrid Materials, National Center of International Joint Research for Hybrid Materials Technology, National Base of International Sci. & Tech. Cooperation on Hybrid Materials, College of Materials Science and Engineering, Qingdao University, Qingdao 266071, PR China
2. Department of Chemical and Biological Engineering, Colorado State University, Fort Collins, Colorado 80523, United States
3. Department of Bioengineering, George Mason University, Fairfax, Virginia 22030, United States