1. Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA.
2. Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA.
3. Carolina Center of Cancer Nanotechnology Excellence, University of North Carolina, Chapel Hill, NC 27599, USA.
4. Institute for Nanomedicine, University of North Carolina, Chapel Hill, NC 27599, USA.
5. Eschelman School of Pharmacy, University of North Carolina, Chapel Hill, NC 27599, USA.