a Institute of Polymer Materials, Department of Material Science and Engineering, Friedrich-Alexander University Erlangen-Nuremberg, Martensstr. 7, 91058 Erlangen, Germany
b Institute of Biomaterials, Department of Material Science and Engineering, Friedrich-Alexander University Erlangen-Nuremberg, Cauerstr. 6, 91058 Erlangen, Germany
Received 25 June 2014, Accepted 29 October 2014, Available online 6 November 2014.