Cardiotoxicity remains a leading cause of clinical trial failure and post-market drug withdrawal. While human iPSC-derived cardiomyocytes (hiPSC-CMs) are increasingly used for preclinical cardiac safety testing, many assays still rely on calcium transient measurements, which provide only indirect information about electrical activity. Voltage-sensitive dyes (VSDs) offer real-time, measurement of action potentials and are as easily adapted to high content screening as calcium measurements. But most available VSDs are prone to photobleaching, motion artifacts, and variable dye loading—challenges that limit reproducibility and scalability. Recently, 3D hiPSC-CM spheroids have been developed as a much more realistic model for cardiotoxicity screening. However, these systems display robust contractility that even more seriously contaminates voltage recordings with large motion artifacts. In this study, we address this problem with dual wavelength ratiometric voltage-sensitive dyes; ratiometric measurements completely eliminate motion artifacts, enabling high fidelity recording of action potential shapes. We have developed a variety of ratiometric VSDs with high quantum efficiency, reduced background interference, and compatibility with both optogenetic pacing and calcium imaging. The red and near infrared spectral properties of some of these new VSDs also make them suitable for use in applications where light scattering and tissue penetration become more challenging. (supported by NIH grant R44GM152985)
Cruz et al. (Sun,) studied this question.