Nanopatterned Nafion Microelectrode Arrays for In Vitro Cardiac Electrophysiology

Jong Seob Choi, Alec S. T. Smith, Nisa P. Williams, Tatsuya Matsubara, Minji Choi, Joon-Wan Kim, Hyung Jin Kim, Seungkeun Choi, Deok-Ho Kim

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Abstract

In this study, nanopatterned Nafion microelectrode arrays for in vitro cardiac electrophysiology are reported. With the aim of defining sophisticated Nafion nanostructures with highly ionic conductivity, fabrication parameters such as Nafion concentration and curing temperature are optimized. By increasing curing temperature and Nafion concentration, the replication fidelity of Nafion nanopatterns when copied from a polydimethylsiloxane master mold are controlled. It is also found that cross-sectional morphology and ion current density of nanopatterned Nafion strongly depends on the fabrication parameters. To investigate this dependency, current-voltage analysis is conducted using organic electrochemical transistors overlaid with patterned Nafion substrates. Nanopatterned Nafion is found to allow higher ion current densities than unpatterned surfaces. Furthermore, higher curing temperatures are found to render Nafion layers with higher ion/electrical transfer properties. To optimize nanopattern dimensions, electrical current flows, and film uniformity, a final configuration consisting of 5% nanopatterned Nafion cured at 65 °C is chosen. Microelectrode arrays (MEAs) are then covered with optimized Nafion nanopatterns and used for electrophysiological analysis of two types of induced pluripotent stem cell-derived cardiomyocytes (iPSCs-CMs). These data highlight the suitability of nanopatterned Nafion, combined with MEAs, for enhancing the cellular environment of iPSC-CMs for use in electrophysiological analysis in vitro.