[1] Univ N Carolina, Joint Dept Biomed Engn, Raleigh, NC 27695 USA
[2] North Carolina State Univ, Raleigh, NC 27695 USA
[3] Univ N Carolina, Eshelman Sch Pharm, Div Mol Pharmaceut, Chapel Hill, NC 27599 USA
[4] Univ N Carolina, Eshelman Sch Pharm, Ctr Nanotechnol Drug Delivery, Chapel Hill, NC 27599 USA
[5] Univ N Carolina, Dept Med, Chapel Hill, NC 27599 USA
[6] NIBIB, Lab Mol Imaging & Nanomed LOM1N, NIH, Bethesda, MD 20892 USA