1. College of Bioresources Chemical and Materials Engineering Shaanxi University of Science and Technology Xi'an 710021 China
2. Polymer Program, Institute of Materials Science University of Connecticut Storrs CT 06269 USA
3. Department of Chemical and Biomolecular Engineering University of Connecticut Storrs CT 06269 USA
4. Department of Biomedical Engineering University of Connecticut Storrs CT 06269 USA