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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. [ABSTRACT FROM AUTHOR]

Tumor cell heterogeneity with distinct phenotypes, genotypes, and epigenetic states as well as the complex tumor microenvironment is major challenges for cancer diagnosis and treatment. There have been substantial advances in our knowledge of tumor biology and in the capabilities of available biological analysis tools; however, the absence of physiologically relevant in vitro testing platforms limits our ability to gain an in‐depth understanding of the role of the tumor microenvironment in cancer pathology. In this review, recent advances in engineered tumor microenvironments to advance cancer research and drug discovery are presented, including tumor spheroids, microfluidic chips, paper scaffolds, hydrogel‐based engineered tissues, 3D bioprinted scaffolds, and multiscale topography. Furthermore, how these technologies address the specific characteristics of the native tumor microenvironment is described. Through the comparison of these biomimetic 3D tumor models to conventional 2D culture models, the validity and physiological relevance of these platforms for fundamental in vitro studies of the tumor biology, as well as their potential use in drug screening applications, is also discussed. [ABSTRACT FROM AUTHOR]