Minimally invasive current-controlled electrical stimulation system for bacteria using highly capacitive conducting polymer-modified electrodes.

This paper proposes a minimally invasive current-controlled electric stimulation system based on a poly(3,4-ethylenedioxythiophene) (PEDOT)-modified electrode to characterize the dynamics of the membrane potential in Bacillus subtilis. A highly capacitive PEDOT-modified electrode enabled the injection of a large ionic charge to the surface of the cells suppressing cytotoxic pH change in the vicinity of the electrode. The current pulse induced a hyperpolarization response in B. subtilis around the electrode. Using quantitative charge injection through current-controlled electrical stimulation, the threshold charge density to excite B. subtilis was roughly estimated to be 530.8 µC cm (of electrode surface area) for the first time. Our results provide the minimum electrical stimulation conditions necessary to minimal invasively control the bacterial membrane potential.