Fluorescence-based system for measurement of electrophysiological changes in stretched cultured cardiomyocytes

Acute or sustained stretch of cardiac tissue is known to play a key role in arrhythmogenesis. Using a fluorescence approach, we designed a system measuring calcium transients and transmembrane potential changes in monolayers of cultured cardiomyocytes under uniaxial elongation and electrical stimulation. Cardiac myocytes are seeded on a rectangular PDMS template held and stretched by a motorized linear guide system. Electrical stimulation is performed with two parallel carbon electrodes supplied by amplified pulses from a digital-to-analog converter. The cells are stained with either voltage- or calcium-sensitive dye (di-4-ANEPPS and Fluo-4 AM respectively). The two available excitation light sources are both current-controlled LED arrays (λ = 523 ± 45 nm for di-4-ANEPPS and λ = 505 ± 15 nm for Fluo-4 AM). The filtered emitted fluorescence (λ > 610 nm for di-4-ANEPPS and λ = 535 ± 25 nm for Fluo-4 AM) is transduced to current with a photodiode, converted to amplified voltage signals and digitized. The design and preliminary validation results are presented.