Aim
We introduce and validate a very low-cost compact mapping system for macroscopic all-optical electrophysiology in layers of hiPSC-CMs. Approach: The system uses oblique transillumination, low-cost cameras, light-emitting diodes, and off-the-shelf components (total <$15,000<$15,000<math><mrow><mo><</mo> <mi>$</mi> <mn>15</mn> <mo>,</mo> <mn>000</mn></mrow> </math> ) to capture voltage, calcium, and mechanical waves under electrical or optical stimulation.
Conclusions
As 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.
Results
Our results corroborate the equivalency of electrical and optogenetic stimulation of hiPSC-CMs, and Vm−[Ca2+]iVm-[Ca2+]i<math> <mrow><msub><mi>V</mi> <mi>m</mi></msub> <mo>-</mo> <mo>[</mo> <msup><mi>Ca</mi> <mrow><mn>2</mn> <mo>+</mo></mrow> </msup> <msub><mo>]</mo> <mi>i</mi></msub> </mrow> </math> 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<0.05mW/mm2<math><mrow><mo><</mo> <mn>0.05</mn> <mtext> </mtext> <msup><mrow><mi>mW</mi> <mo>/</mo> <mi>mm</mi></mrow> <mrow><mn>2</mn></mrow> </msup> </mrow> </math> ). Measurements in warmer culture medium yield larger spread of action potential duration and higher conduction velocities compared to Tyrode's solution at room temperature. Conclusions: As 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.
Significance
All-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. Aim: We introduce and validate a very low-cost compact mapping system for macroscopic all-optical electrophysiology in layers of hiPSC-CMs. Approach: The system uses oblique transillumination, low-cost cameras, light-emitting diodes, and off-the-shelf components (total <$15,000<$15,000<math><mrow><mo><</mo> <mi>$</mi> <mn>15</mn> <mo>,</mo> <mn>000</mn></mrow> </math> ) to capture voltage, calcium, and mechanical waves under electrical or optical stimulation. Results: Our results corroborate the equivalency of electrical and optogenetic stimulation of hiPSC-CMs, and Vm−[Ca2+]iVm-[Ca2+]i<math> <mrow><msub><mi>V</mi> <mi>m</mi></msub> <mo>-</mo> <mo>[</mo> <msup><mi>Ca</mi> <mrow><mn>2</mn> <mo>+</mo></mrow> </msup> <msub><mo>]</mo> <mi>i</mi></msub> </mrow> </math> 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<0.05mW/mm2<math><mrow><mo><</mo> <mn>0.05</mn> <mtext> </mtext> <msup><mrow><mi>mW</mi> <mo>/</mo> <mi>mm</mi></mrow> <mrow><mn>2</mn></mrow> </msup> </mrow> </math> ). Measurements in warmer culture medium yield larger spread of action potential duration and higher conduction velocities compared to Tyrode's solution at room temperature. Conclusions: As 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.