1. Department of Pharmaceutical Engineering, College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, Hunan Province, P. R. China
2. Department of Pharmaceutics, Xiangya School of Pharmaceutical Sciences, Central South University, Changsha 410013, Hunan Province, P. R. China
3. Molecular Imaging Research Center of Central South University, Changsha 410008, Hunan Province, P. R. China