Controlling the Resting Membrane Potential of Cells with Conducting Polymer Microwires.

All cells have a resting membrane potential resulting from an ion gradient across the plasma membrane. The resting membrane potential of cells is tightly coupled to regeneration and differentiation. The ability to control this parameter provides the opportunity for both biomedical advances and the probing of fundamental bioelectric pathways. The use of poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) conducting polymer microwires to depolarize cells is tested using E. coli cells loaded with a fluorescent dye that is pumped out of the cells in response to depolarization; a more positive membrane potential. Fluorescence imaging of the cells in response to a conducting-polymer-microwire applied voltage confirms depolarization and shows that the rate of depolarization is a function of the applied voltage and frequency. Microwire activity does not damage the cells, demonstrated with a propidium iodide assay of membrane integrity. The conducting polymer microwires do not penetrate the cell, or even come into contact with the cell; they only need to generate a minimum electric field, controlled by the placement of the wires. It is expected that these microwires will provide a new, noninvasive, cellular-scale tool for the control of resting membrane potential with high spatial precision.