1 Fraunhofer Institute for Cell Therapy and Immunology, Branch Bioanalytics and Bioprocesses, Am Mühlenberg 13, 14476 Potsdam-Golm, Germany. Anna.Vikulina@izi-bb.fraunhofer.de.
2 School of Science and Technology, Nottingham Trent University, Clifton Lane, Nottingham NG11 8NS, UK. Dmitry.Volodkin@ntu.ac.uk.