1. Interdisciplinary Nanoscience Centre, Aarhus University, Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark, and NSM, Research Unit for Functional Biomaterials, Roskilde University, Building 18.1, DK-4000 Roskilde, Denmark, and Department of Life Sciences, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg