1. Department of Medicine, Division of NanoMedicine, ‡Center for Environmental Implications of Nanotechnology, California NanoSystems Institute, §Department of Chemistry and Biochemistry, ⊥Electron Microscopy Core Facility, California NanoSystems Institute, ∥Department of Molecular, Cell, and Developmental Biology, #Department of Materials Science and Engineering, ∇California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California 90095, United States