title: Fabrication and characterization of a K⁺-selective nanoelectrode and simultaneous imaging of topography and local K⁺ flux using scanning electrochemical microscopy.
abstract: A nanopipette containing a solution of bis(benzo-15-crown-5) dissolved in 1,6-dichlorohexane was used as an ion-selective electrode (ISE) to probe K(+) for shear force-based constant-distance scanning electrochemical microscopy (SECM). In a previous study, the ISE responded only at low K(+) concentrations ([K(+)] < 1 mM), due to the depletion of the bis(benzo-15-crown-5) at the oil/water interface at high K(+) concentrations and the unstable response of the tip at the oil/water interface for shear force and current detection. In the present study, a nanopipette reshaped by heating and with the hydrophobic layer removed was used as the ISE. This modified ISE enabled a rapid response to changes in K(+) flux at a physiological concentration of K(+) and allowed SECM imaging on a nanometer scale. The fabricated nano-ISE was used as a probe for shear force-based SECM. Topography and K(+) flux images were obtained simultaneously at a polycarbonate membrane filter with 5 μm pores and human embryonic kidney 293 cells (HEK293). Several areas containing a K(+) flux larger than the surrounding areas were found in the SECM images of the HEK293 cells, which indicated the existence of K(+) channels.
authors.affiliation: Department of Applied Chemistry, National Defense Academy , 1-10-20 Hashirimizu, Yokosuka, Kanagawa 239-8686, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamada
authors.forename: Daiki
authors.initials: D
authors.lastname: Haraguchi
authors.forename: Kenji
authors.initials: K
authors.lastname: Yasunaga
mesh_terms: D055664:Electrochemical Techniques; D057809:HEK293 Cells; D006801:Humans; D017736:Ion-Selective Electrodes; D007477:Ions / Q000737:chemistry; D064347:Microscopy, Electrochemical, Scanning; D036103:Nanotechnology; D009821:Oils / Q000737:chemistry; D011188:Potassium / Q000032:analysis*; D014867:Water / Q000737:chemistry
chemical_list: D007477:Ions; D009821:Oils; D014867:Water; D011188:Potassium