Transport process across epithelia takes place by either active transcellular pathways or passive paracellular pathways. At cell-cell junctions, paracellular pathways consist of tight junctions (TJs) regulated by TJ proteins and can be mediated by addition of some drug molecules. These molecules can directly modulate TJs to open/close paracellular spaces or change extracellular conditions to affect the expression of TJ proteins. However, defined mechanisms are still unclear for many of them. To measure the effect of a specific drug on paracellular transport, techniques using Ussing chamber and two-path impedance spectroscopy can be utilized to monitor paracellular conductance/resistance. While informative, they are not able to collect characteristic responses from a single cell, or the permeability change at small but important subcellular structures like tricellular TJs. Recently, our group has developed potentiometric scanning ion conductance microscopy (P-SICM) to record local conductance of cell samples at subcellular resolution. It utilizes a double-barrel nanoscale pipette and the ability of scanning ion conductance microscopy (SICM) to precisely control the position of the pipette over cell monolayer and measure the local potential generated by cell features, from which local conductance information can be calculated. Our previous work combined P-SICM with hopping mode techniques to allow simultaneous nanometer-scale conductance and topography mapping, which makes visualization of ion transport through subcellular structures possible. In this study, we make use of P-SICM conductance mapping to study transport properties of single cells under the influence of absorption enhancer sodium caprate and blood osmolality regulator mannitol respectively, with paracellular conductance and even tricellular conductance resolved. Time/Dose-response curves and recovery processes after removal of drug molecules are recorded. This study will potentially provide more information on the way drug molecules alter paracellular pathways and insights for daily dose.

Monitoring the response of epithelial cells to drug molecules with potentiometric-scanning ion conductance microscopy

256th National Meeting (2018)

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