Dielectrophoretic estimation of resting membrane potential in excitable cells

The cell membrane potential (Vm) is of paramount significance in cell electrophysiology, most notably in excitable cells found in muscle and nervous tissues. Vm is the voltage between the cell interior and extracellular space, and arises due to the diffusion potentials of potassium, chloride and sodium across the membrane. We recently reported a method to determine the resting membrane potential (RMP) of non-excitable cells including blood cells, chondrocytes, macrophages, and cancer cells, using a label-free, non-destructive, high-throughput method based on the electrical phenomenon dielectrophoresis (DEP). In this manuscript, we extend this technique to include the principal excitable cells, by altering the model to account for the different mechanisms which generate Vm in these cells. Our results indicate that unlike the RMP in non-excitable cells, excitable cells may have a smaller potential measured across the membrane itself, with sizeable extracellular component of Vm across the electrical double layer, measurable in the cell ζ-potential. When this was accounted for, the adapted model yielded results comparable to values in the literature. The model produced estimated values of RMP of -71.8 mV for SH-SY5Y neuroblastoma cells, and -74.2 mV in H9c2 cardiomyoblasts. Moreover, analysis of cardiomyoblasts in media with low concentrations of extracellular ions suggests that DEP can yield estimates of RMP in these media which align with published data for myocytes, with values of -54.1 mV between 100-600 mSm-1 and +12.7 mV below 100 mSm-1. This suggests that not only is DEP capable of accurate determination of Vm across the full range of cell types, but also that it could be used to examine ion channel behaviour and its effect on Vm across many ion concentrations.