1. Center for Nanotechnology in Drug Delivery, Division of Molecular Pharmaceutics, Eshelman School of Pharmacy; University of North Carolina at Chapel Hill; Chapel Hill NC 27599-7362 USA
2. Department Chemie; Technische Universität Dresden; Zellescher Weg 19 01069 Dresden Germany
3. Center for Drug Delivery and Nanomedicine and Department of Pharmaceutical Sciences, College of Pharmacy; University of Nebraska Medical Center; Omaha NE 68198-5830 USA
4. Functional Polymer Materials, Chair for Chemical Technology of Materials Synthesis, Department Chemistry and Pharmacy; Julius-Maximilians-Universität Würzburg; Röntgenring 11 97070 Würzburg Germany
5. Laboratory of Chemical Design of Bionanomaterials, Faculty of Chemistry; M.V. Lomonosov Moscow State University; Moscow 119992 Russia