title: Topographical and electrochemical nanoscale imaging of living cells using voltage-switching mode scanning electrochemical microscopy.
abstract: We describe voltage-switching mode scanning electrochemical microscopy (VSM-SECM), in which a single SECM tip electrode was used to acquire high-quality topographical and electrochemical images of living cells simultaneously. This was achieved by switching the applied voltage so as to change the faradaic current from a hindered diffusion feedback signal (for distance control and topographical imaging) to the electrochemical flux measurement of interest. This imaging method is robust, and a single nanoscale SECM electrode, which is simple to produce, is used for both topography and activity measurements. In order to minimize the delay at voltage switching, we used pyrolytic carbon nanoelectrodes with 6.5-100 nm radii that rapidly reached a steady-state current, typically in less than 20 ms for the largest electrodes and faster for smaller electrodes. In addition, these carbon nanoelectrodes are suitable for convoluted cell topography imaging because the RG value (ratio of overall probe diameter to active electrode diameter) is typically in the range of 1.5-3.0. We first evaluated the resolution of constant-current mode topography imaging using carbon nanoelectrodes. Next, we performed VSM-SECM measurements to visualize membrane proteins on A431 cells and to detect neurotransmitters from a PC12 cells. We also combined VSM-SECM with surface confocal microscopy to allow simultaneous fluorescence and topographical imaging. VSM-SECM opens up new opportunities in nanoscale chemical mapping at interfaces, and should find wide application in the physical and biological sciences.
authors.affiliation: World Premier International Research Center-Advanced Institute for Materials Research, Tohoku University, Katahira, Aoba 2-1-1, Sendai 980-8577, Japan. takahashi@bioinfo.che.tohoku.ac.jp
authors.forename: Yasufumi
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Andrew I
authors.initials: AI
authors.lastname: Shevchuk
authors.forename: Pavel
authors.initials: P
authors.lastname: Novak
authors.forename: Babak
authors.initials: B
authors.lastname: Babakinejad
authors.forename: Julie
authors.initials: J
authors.lastname: Macpherson
authors.forename: Patrick R
authors.initials: PR
authors.lastname: Unwin
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Shiku
authors.forename: Julia
authors.initials: J
authors.lastname: Gorelik
authors.forename: David
authors.initials: D
authors.lastname: Klenerman
authors.forename: Yuri E
authors.initials: YE
authors.lastname: Korchev
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Matsue
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D003952:Diagnostic Imaging / Q000379:methods*; D055664:Electrochemical Techniques / Q000379:methods*; D004566:Electrodes; D005453:Fluorescence; D006801:Humans; D020527:Microscopy, Scanning Probe / Q000379:methods*; D049329:Nanostructures / Q000737:chemistry*; D016716:PC12 Cells; D051381:Rats; D013997:Time Factors