[1] Univ N Carolina, Joint Dept Biomed Engn, Chapel Hill, NC 27514 USA
[2] N Carolina State Univ, Raleigh, NC 27695 USA
[3] Univ N Carolina, Eshelman Sch Pharm, Ctr Nanotechnol Drug Delivery, Chapel Hill, NC USA
[4] Univ N Carolina, Eshelman Sch Pharm, Div Mol Pharmaceut, Chapel Hill, NC USA
[5] Nanjing Univ, Dept Polymer Sci & Engn, Sch Chem & Chem Engn, Nanjing 210008, Jiangsu, Peoples R China