1. Cancer Research Center; Sanford Burnham Prebys Medical Discovery Institute; La Jolla CA 92037 USA
2. Department of Surgery; Herbert Irving Comprehensive Cancer Center; Columbia University College of Physicians and Surgeons; New York NY 10032 USA
3. Center for Nanomedicine and Department of Molecular, Cellular and Developmental Biology; University of California; Santa Barbara CA 93106 USA
4. Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems; School of Materials Science and Engineering; Beijing Institute of Technology; Beijing 100081 P. R. China
5. Moores Cancer Center; Department of Radiology; University of California; San Diego, La Jolla CA 92093 USA
6. Department of Chemistry and Biochemistry; University of California; San Diego, La Jolla CA 92093 USA
7. Research Center of Materials Science; Beijing Institute of Technology; Beijing 100081 P. R. China