1. Shaanxi Key Laboratory of Degradable Biomedical Materials School of Chemical Engineering Northwest University Xi'an Shaanxi 710069 China
2. Shaanxi R&D Centre of Biomaterials and Fermentation Engineering School of Chemical Engineering Northwest University Xi'an Shaanxi 710069 China
3. Biotech. and Biomed. Research Institute Northwest University Xi'an Shaanxi 710069 China