1. Sino-German Nano-Analytical Laboratory (SiGNAL), Department of Chemistry, and the Bioengineering Graduate Program, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, Department of Bioengineering and Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore, and Institute of Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Strasse 24−25, 14476 Golm, Germany