1. Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, United States
2. Institute for NanoBioTechnology, Johns Hopkins University, Baltimore, Maryland 21218, United States
3. Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, United States
4. Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, United States
5. Cancer Targeting Systems, Chesterford Research Park, Cambridge CB10 1XL, U.K.
6. Translational Tissue Engineering Center, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, United States