Potentiometric scanning ion conductance microscopy (P-SICM) is a novel tool that is able to differentiate para and trans cellular pathways conductance in epithelial cell layers. This technique measures variation in potential generated at a surface with a dual-barrel probe design. One barrel is used as distance control by maintaining a constant ion current and the second barrel measures potential difference. Different from bulk measurement, P-SICM provides localized information by positioning pipet over different spots on a surface with a small probe-surface distance. Also, due to the precise feedback control given by SICM, P-SICM is able to utilize a much smaller pipet and probe-surface distance compared to traditional voltage scanning technique. However, the ion current for distance control and the small probe-surface distance make the system more complex. Therefore, to study the effect on the measured conductance from the unique features in SICM, a porous membrane with pores milled by Focused Ion Beam (FIB) is utilized as a simplified model for cell membranes. By measuring potential responses with different probe-surface distance, pore sizes, pipet current and pipet sizes, the detailed mechanism of P-SICM is understood. Data interpretation is more quantitative with exact geometry and property known in the system and proposed circuit model. By studying a FIB standard, the mechanism of the new technique P-SICM is understood providing guidance for more quantitative studies with biological sample.

Potentiometric scanning ion conductance microscopy

246th National Meeting (2013)

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