Portable low-cost macroscopic mapping system for all-optical cardiac electrophysiology

Abstract

SignificanceAll-optical cardiac electrophysiology enables the visualization and control of key parameters relevant to the detection of cardiac arrhythmias. Mapping such responses in human induced pluripotent stem-cell-derived cardiomyocytes (hiPSC-CMs) is of great interest for cardiotoxicity and personalized medicine applications. AimWe introduce and validate a very low-cost compact mapping system for macroscopic all-optical electrophysiology in layers of hiPSC-CMs. ApproachThe system uses oblique trans-illumination, low-cost cameras, light-emitting diodes and off-the-shelf components (total < $15,000) to capture voltage, calcium and mechanical waves under electrical or optical stimulation. ResultsOur results corroborate the equivalency of electrical and optogenetic stimulation of hiPSC-CMs, and Vm - [Ca2+]i similarity in conduction under pacing. Green-excitable optical sensors are combinable with blue optogenetic actuators (Chanelrhodopsin2) only under very low green light (< 0.05mW/mm2). Measurements in warmer culture medium yield larger spread of action potential duration and higher conduction velocities compared to Tyrodes solution at room temperature. ConclusionsAs multiple optical sensors and actuators are combined, our results can help handle the "spectral congestion" and avoid parameter distortion. We illustrate the utility of the system for uncovering the action of cellular uncoupling agents and show extensibility to an epi-illumination mode for future imaging of thicker native or engineered tissues.