1. a Institute of Biophysics, Bulgarian Academy of Science, Akad. G. Bonchev Str. Bl. 21, 1113 Sofia, Bulgaria
2. b GKSS Research Center, Institute of Polymer Research, Kantstrasse 55, 14513 Teltow, Germany
3. c GKSS Research Center, Institute of Polymer Research, Kantstrasse 55, 14513 Teltow, Germany
4. d GKSS Research Center, Institute of Polymer Research, Kantstrasse 55, 14513 Teltow, Germany
5. e Biomedical Materials Group, Dept. Pharmaceutics and Biopharmaceutics, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Strasse 1, 06120 Halle (Saale), Germany
6. f GKSS Research Center, Institute of Polymer Research, Kantstrasse 55, 14513 Teltow, Germany
7. g ICREA and Institute for Bioengineering of Catalonia, Parc Scientific de Barcelona, Josep Samitier 1/5, 08028 Barcelona, Spain