Amperometric ion-selective nanoelectrodes for bioanalytical sensing and imaging.

This review is focused on the recent applications of amperometric ion-selective nanoelectrodes as emerging electrochemical methods for bioanalytical sensing and imaging. The amperometric nanoelectrodes offer advantages over the potentiometric counterparts toward unprecedented in-vitro and in-vivo ion analysis of biological systems. The amperometric nanoelectrodes serve not only as electrochemical ion sensors based on highly selective ionophores but also as the tips of scanning electrochemical microscopy (SECM) to enable ion imaging with a spatial resolution of down to 30 nm. Moreover, the high biocompatibility and simple fabrication of ion-selective nanopipets and micropipets are attractive for in vivo bioanalysis. Specifically, we will introduce the principle of amperometric ion-selective nanoelectrodes as well as nanoscale SECM for bioanalytical sensing and imaging, respectively. Applications of amperometric ion-selective nanoelectrodes are exemplified by nanoscale SECM imaging of molecular transport at the single nuclear pore complex and chemical interactions among single bacterial cells. The powerful sensing applications of amperometric ion-selective nanoelectrodes are illustrated for the detection of carbonate generated by bacterial cells as well as both in-vitro and in-vivo detection of neurotransmitter acetylcholine.