1 Institut of Pharmaceutics and Biopharmaceutics, Heinrich Heine University Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany.
2 Institute of Electron Microscopy and Nanoanalysis and Center for Electron Microscopy, Graz University of Technology, NAWI Graz, Steyrergasse 17, 8010 Graz, Austria.
3 Center of Advanced Imaging, Heinrich Heine University, Universitätsstraße 1, 40225 Düsseldorf, Germany.
4 Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology and Biopharmacy, Karl Franzens University Graz, Universitätsplatz 1, 8010 Graz, Austria.
5 Institut of Pharmaceutics and Biopharmaceutics, Heinrich Heine University Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany. Electronic address: Joerg.breitkreutz@hhu.de.