1. National Center for Nanoscience and Technology; Beijing 100190 China
2. Department of Molecular and Medical Pharmacology; Crump Institute for Molecular Imaging (CIMI); California NanoSystems Institute (CNSI); University of California; Los Angeles CA 90095-1770 USA
3. School of Biomedical Engineering; MED-X Research Institute; Shanghai Jiao Tong University; Shanghai 200030 China
4. Department of Human Genetics; David Geffen School of Medicine; University of California Los Angeles; Los Angeles CA 90095-7088
5. Molecular Biology Institute; Microbiology, Immunology, and Molecular Genetics; University of California Los Angeles; Los Angeles CA 90024 USA