1 Institute of Biological Chemistry, Biophysics and Bioengineering, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K.
2 The Institute of Sensor and Actuator Technology (ISAT), 96450 Coburg, Germany.
3 Infection Medicine, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9YL, U.K.