Simultaneous Electrical and Fluorescence Recording of HL-1 cells' Electrical Activity in Response to Extracellular Calcium Stimulation

In current cell tissue engineering and cardiology, beating models with behavior and properties similar to humans are necessary. The cardiac muscle HL-1 cells, whose genes have a parent with adult atrial myocytes, serve as a suitable model. HL-1 cells were seeded on a 120-electrode microelectrode (MEA) chamber and transient transfection of Accelerated Sensor of Action Potentials 1 (ASAP1), a genetically encoded voltage indicator, was performed. Simultaneous electrical and optical recording of cardiac cell culture electrical activity was made when the cells started to produce spontaneous action potentials. Recording synchronization was made using TTL pulses. Results showed that HL-1 cells start to produce asynchronous spontaneous action potentials (-375±10μV) when reaching 90% MEA chamber confluency and which become periodical addition of extracellular calcium (-501±14 μV, 2.1±1.0 Hz). The ASAP1's fluorescent response reached up to 21±5% ΔF/F. The time constant between detection of electrical and fluorescent response (τe/0) was determined as 12±5 ms.