1. California NanoSystems Institute Crump Institute for Molecular Imaging Department of Molecular and Medical Pharmacology University of California, Los Angeles Los Angeles CA 90095 USA
2. Beijing National Laboratory for Molecular Sciences MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering College of Chemistry and Molecular Engineering Peking University Beijing 100871 P. R. China
3. Department of Pathology and Immunology School of Medicine Washington University in St. Louis St. Louis MO 63110 USA
4. Department of Pathology The First Affiliated Hospital Sun Yat‐sen University Guangzhou Guangdong 510080 P. R. China