1. Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21202, United States
2. Department of Nanoengineering, University of California San Diego, La Jolla, California 92093, United States
3. Biochemistry, Cellular and Molecular Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21202, United States
4. Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts 02215, United States
5. Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Allston, Massachusetts 02134, United States