Extracellular Photovoltage Clamp Using Conducting Polymer‐Modified Organic Photocapacitors

Abstract Optoelectronic control of physiological processes accounts for new possibilities ranging from fundamental research to treatment of disease. Among nongenetic light‐driven approaches, organic semiconductor‐based device platforms such as the organic electrolytic photocapacitor (OEPC) offer the possibility of localized and wireless stimulation with a minimal mechanical footprint. Optimization of efficiency hinges on increasing effective capacitive charge delivery. Herein, a simple strategy to significantly enhance the photostimulation performance of OEPC devices by employing coatings of the conducting polymer formulation poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate), or PEDOT:PSS is reported. This modification increases the charge density of the stimulating photoelectrodes by a factor of 2–3 and simultaneously decreases the interfacial impedance. The electrophysiological effects of PEDOT:PSS‐derivatized OEPCs on Xenopus laevis oocyte cells on membrane potential are measured and voltage‐clamp techniques are used, finding an at‐least twofold increase in capacitive coupling. The large electrolytic capacitance of PEDOT:PSS allows the OEPC to locally alter the extracellular voltage and keep it constant for long periods of time, effectively enabling a unique type of light‐controlled membrane depolarization for measurements of ion channel opening. The finding that PEDOT:PSS‐coated OEPCs can remain stable after a 50‐day accelerated ageing test demonstrates that PEDOT:PSS modification can be applied for fabricating reliable and efficient optoelectronic stimulation devices.