1. MIRA Institute for Biomedical Technology and Technical Medicine, Department of Polymer Chemistry and Biomaterials, University of Twente, P.O. Box 217, 7500 AE, Enschede, The Netherlands
2. MESA+ Institute for Nanotechnology and Laboratory of Supramolecular Chemistry and Technology, University of Twente, P.O. Box 217, 7500 AE, Enschede, The Netherlands
3. Department of Biomedical Engineering, University Medical Centre Groningen and University of Groningen, P.O. Box 196, 9700 AD Groningen, The Netherlands