Ilya Reviakine1, Steffen Braune2. 1. Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany And Department of Bioengineering, University of Washington, Seattle, Washington 98105. 2. Department of Biointerface Engineering, Institute of Biomaterial Science, Helmholtz-Zentrum Geesthacht, Kantstrasse 55, 14513 Teltow, Germany.