Abstracts

CHARACTERIZATION OF LIGHT-ACTIVATED CALCIUM CURRENT VIA NATIVE CARDIAC CAV1.2 CHANNELS USING ORGANIC PHOTOCAPACITORS

Niroj Shrestha1, Sara Stoppacher2, Mathias Polz2, Klaus Zorn-Pauly1, Brigitte Pelzmann1, Theresa Rienmüller2, Muammer Üçal3, Karin Kornmüller2, Ludovico Migliaccio4, Vedran Đerek5, Eric Głowacki4, Susanne Scheruebel1.

1Gottfried Schatz Research Center-Biophysics, Medical University of Graz, Austria; 2Institute of Health Care Engineering with European Testing Center of Medical Devices, Graz University of Technology, Austria; 3Department of Neurosurgery, Medical University of Graz, Austria; 4Bioelectronics Materials and Devices, Central European Institute of Technology, Czech Republic; 5Department of Physics, Faculty of Science, University of Zagreb, Bijenička c. 32, 10000 Zagreb, Croatia.

Organic photocapacitors or photocaps consist of transparent donor-acceptor bilayer of organic semiconductors. They have been reported previously to act as extracellular capacitive electrodes for depolarizing cell membrane and activating overexpressed potassium channels in oocytes upon light illumination of 660 nm. Here, we investigated the photocap-mediated activation of calcium current via native voltage-gated Cav1.2 channels (ICa,L) in guinea pig ventricular cardiomyocytes. Photocaps with 13 mm diameter PN layer on top of 25 mm ITO back electrode on PET foil was coated with PEDOT:PSS to enhance the electrolytic capacitance of photocaps. Using whole-cell patch-clamp technique, cardiomyocyte on photocap was clamped to -40 mV and upon voltage depolarizing step to 0 mV for 100 ms, ICa,L was activated, as reported previously. Light stimulation for 100 ms activated ICa,L similar in amplitude to that observed with the voltage step. Nifedipine, a L-type calcium channel blocker, inhibited this current activation, further supporting light-induced cell depolarization and ICa,L activation. Besides, the light-induced Cav1.2 channel inactivation showed similar kinetic parameters to that of voltage-induced inactivation. Modeling of Cav1.2 channels is being carried out to characterize the activation and inactivation parameters of light-induced ICa, L in cardiac cells on photocaps.

Presenting author e-mail address: niroj.shrestha@medunigraz.at