1. Key Laboratory of Drug-Targeting and Drug Delivery System of the Education Ministry and Sichuan Province, West China School of Pharmacy, Sichuan University, No. 17 Section 3, Southern Renmin Road, Chengdu 610041, P. R. China
2. Department of Pharmaceutical & Biological Engineering, School of Chemical Engineering, Sichuan University, No. 24 South Section 1, Yihuan Road, Chengdu 610065, P. R. China