Two-Electrode Voltage Clamp (TEVC) Based Scanning Ion Conductance Microscopy: New Methodology and Validation
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Scanning ion conductance microscopy (SICM) is a scanning probe technique that utilizes an electrolyte filled glass-pipette to recover the topography of a non-conductive sample in an electrolyte solution. This technique monitors the change in current that is caused by a change of resistance through the pipette to recover the topographic image of a non-conductive sample. By monitoring the change in current, the probe does not actually come in contact with the sample such as the Atomic Force Microscope, which makes contact and deforms the sample in doing so. SICM has shown potential in various applications such as high resolution imaging of living biological cells or the determination of local changes on the cellular level. SICM can be combined with other imaging techniques such as fluorescence microscopy, confocal microscopy, and patch clamping. A key feature of SICM is its non-invasive scanning ability. The ability to scan samples without coming making contact allows for more robust research in biology. Current SICM techniques call for a one electrode probe, but in this research we are exploring a two-electrode scanning apparatus. With a two-electrode approach, the two-electrode voltage clamp (TEVC) technique is utilized. TEVC is typically used in electrophysiological experiments to control the membrane potential and study properties of ion channels. Advantages of a two-electrode approach is its high current-passing capacity, the ability to inject current into the system based on the measurement feedback, thus increasing its sensitivity and signal-to-noise ratio. By having a noise-compensation system, scans do not need to be in a strictly controlled low-noise environment. Comparing with the single-electrode system, this new system can handle high current-capacity measurements and is inherently insensitive to noise which is the challenge of measuring small currents. This research will explore the ability to recover topographic images of non-conductive samples using this two-electrode approach.