Scanning electrochemical microscopy for imaging single cells and biomolecules

This article presents an overview of the recent progress in scanning electrochemical microscopy (SECM) for imaging single cells and biomolecules. SECM is a technique for characterizing the local electrochemical nature of various materials by scanning a probe microelectrode. The probe current reflects the electrochemical processes occurring in the small space surrounded by the probe and the substrate. The spatial resolution of SECM is inferior to conventional scanning probe microscopes such as scanning tunneling microscopy (STM) and atomic force microscopy (AFM), since the fabrication of the probe microelectrodes with nanometer sizes is quite difficult. However, recent progress in the fabrication of nanometer-scale electrodes and the development of electrode-sample distance control systems has greatly enhanced the capacity of SECM systems to solve problems in cell biology. The topics reviewed include the following: enzyme activity evaluation, electrochemical enzyme-linked immunosorbent assays, membrane permeability evaluation, respiratory activity measurements, reporter gene assays, membrane protein imaging, and neurotransmitter detection.