1. Department of Pharmacology
2. Institute of Basic Medical Sciences
3. Chinese Academy of Medical Sciences & Peking Union Medical College
4. Beijing 100005, P. R. China
5. CAS Key Laboratory of Standardization and Measurement for Nanotechnology
6. National Center for Nanoscience and Technology
7. Beijing 100190, P. R. China
8. Department of Biomedical Engineering
9. Beijing, P. R. China