Cardiomyopathies, heart failure, and arrhythmias or conduction blockages impact millions of patients worldwide and are associated with marked increases in sudden cardiac death, decreased quality of life, and sequelae or complications. These pathologies stem from dysfunction in the contractile or conductive properties of the cardiomyocyte (CM), which is a focus of fundamental investigation, drug discovery, and therapeutic development. Separate from direct disease impact, pharmaceutical cardiotoxicity or lack of efficacy during both clinical trials and marketing is a leading reason for clinical trial failure or post-release drug recalls, ostensibly due to inadequate predictivity by existing animal or in vitro models. In terms of in vitro models, both animals and pluripotent stem cells offer sources of cardiomyocytes for such specific applications. Murine adult cardiomyocytes are a workhorse model for basic science but are physiologically delicate and degrade rapidly in culture;​ pluripotent stem cell-derived cardiomyocytes (PSC-CMs) offer an inexhaustible source of human CMs but are immature in all aspects of functional physiology. Furthermore, with the advent of engineered tissues and lab-on-a-chip systems, certain well-established experimental workflows to address advanced or emergent physiology in situ or ex vivo have yet to be adapted to high-throughput or microfluidic applications.

In this thesis, two highly-functional cardiomyocyte models are introduced, including an isolated adult murine CM model that retains function in culture, and an induced pluripotent stem cellderived CM that has been matured using a novel cell culture formulation beyond the function attainable with existing gold-standard CM media. Both culture models are characterized by several well-defined biochemical and imaging techniques, but also in a number of specific functional metrics including Ca²⁺ handling and drug sensitivity, contractility, respirometric performance, and in the latter, global proteomics and RNA sequencing. Furthermore, a novel meta-analysis of transcriptomic datasets presents a landscape of CM maturation strategies, and introduces new questions in how to both define and achieve PSC-CM maturation in vitro. Finally, this thesis presents the design, prototyping, and cell-free validation of in silico characterization of an intermittent-flow respirometer for engineered tissues, including myocardial organoid models. Together, these works serve as a well-characterized toolbox, both for use in basic science applications, as well as a basis for further optimization and enhancement by tissue engineers.