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−2 (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. © 2022 Elsevier B.V.