Kostov, Y., Entcheva E., Tchernev E., Tung L., (2004) Fluorescence Imaging of Electrical Activity in Cardiac Cells Using An All-Solid-State System. IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING. VOL. 51, NO. 2
Tracking spatial and temporal determinants of cardiac arrhythmogenesis at the cellular level presents challenges to the optical mapping techniques employed. In this paper, we describe a compact system combining two nontraditional low-cost solutions for excitation light sources and emission filters in fluorescence measurements of transmembrane potentials, Vm, or intracellular calcium, [Ca2+]i in cardiac cell networks. This is the first reported use of high-power blue and green light emitting diodes (LEDs), to excite cell monolayers stained withVm- (di-8-ANEPPS) or [Ca2+]i – (Fluo-3) sensitive dyes. In addition, we use simple techniques for fabrication of suitable thin emission filters with uniform properties, no auto-fluorescence, high durability and good flexibility for imagingVm or [Ca2+]i . The battery-operated LEDs and the fabricated emission filters, integrated with a fiber-optic system for contact fluorescence imaging, were used as tools to characterize conduction velocity restitution at the macro-scale. The versatility of the LEDs for illumination is further emphasized through 1) demonstration of their usage for epi-illumination recordings at the single-cell level, and 2) demonstration of their unique high-frequency light modulation ability. The LEDs showed excellent stability as excitation light sources for fluorescence measurements; acceptable signal-to-noise ratio and negligible cell photodamage and indicator dye photobleaching were observed.