Optoelectronic control of single cells using organic photocapacitors

Abstract

Optical control of the electrophysiology of single cells can be a powerful tool for biomedical research and technology. Here, we report organic electrolytic photocapacitors (OEPCs), devices that function as extracellular capacitive electrodes for stimulating cells. OEPCs consist of transparent conductor layers covered with a donor-acceptor bilayer of organic photoconductors. This device produces an open-circuit voltage in a physiological solution of 330 mV upon illumination using light in a tissue transparency window of 630 to 660 nm. We have performed electrophysiological recordings on Xenopus laevis oocytes, finding rapid (time constants, 50 μs to 5 ms) photoinduced transient changes in the range of 20 to 110 mV. We measure photoinduced opening of potassium channels, conclusively proving that the OEPC effectively depolarizes the cell membrane. Our results demonstrate that the OEPC can be a versatile nongenetic technique for optical manipulation of electrophysiology and currently represents one of the simplest and most stable and efficient optical stimulation solutions.

Extracellular Photovoltage Clamp Using Conducting Polymer‐Modified Organic Photocapacitors

“…Measurements of photovoltage and charging current of OEPC devices was performed according to previously described methods 17. Briefly, the backside ITO of the OEPC was contacted with a probe electrode connected to the positive terminal of an oscilloscope.…”

“…The efficacy of OEPCs in neuromodulation was shown for cultured neurons and explanted retinal tissues where OEPCs stimulate direct action potentials in retinal ganglion cells of blind chick retinas 16. More recently, the potential of OEPCs was validated by measuring large depolarizations of the membrane potential of Xenopus laevis oocytes, and accompanying opening of voltage‐gated channels 17. Advantages of the OEPC include that they are fabricated from biocompatible and nontoxic components, and are ultrathin, in the range of tens to hundreds of nanometers.…”

Plasmon-Coupled Photocapacitor Neuromodulators

“…To test the biological and electrophysiological activity we used SHSY-5Y cells. These kinds of non-spiking cells such as N2A, oocytes are already used to prove the neuromodulation ability [26, 27]. Initially, we tested the mitochondrial activity with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays to determine the toxicity of the plasmonic biointerfaces on SHSY-5Y cell line.…”

“…cm −2 light sensitivity of plasmonic biointerface corresponds to more than 3 orders of magnitude smaller than ocular safety limits (see Methods section). Though the transmembrane potential variation in the free membrane seems low, the variation in the attached membrane is significantly larger [27], moreover the current levels (over 100 pA) that are observed by using similar electrophysiological measurements [29] are enough to elicit action potentials. Therefore, these plasmonic biointerfaces are potentially applicable to recover the vision due to photoreceptor loss in the retina [6].…”

Biological Considerations of Optical Interfaces for Neuromodulation

“…The voltage perturbation was proportional to the size of the semiconductor interface and required a diameter of at least 100 µm, which is equivalent in size to many electrodes currently employed for deep brain stimulation. Subsequently, interfaces made using this technique were shown to produce significant depolarizations in oocytes over periods of up to 180 days …”