In this video, spontaneously beating human stem cell-derived cardiomyocytes stained with ElectroFluor630^TM (aka Di-4-ANEQ(F)PTEA) allows ratiometric optical action potential recordings. The ratio of two excitation wavelengths boosts signals and removes artifacts due to non-uniform staining, bleaching, and the motion of these beating (contracting) human heart cells in a dish.

Optical electrophysiology in vivo pig model. Ratio imaging solves the motion problem during beats. New fluorinated long wavelength VSD facilitates loading and has low toxicity. Large animal model is a key step toward human imaging.

Key products and applications

Di-4-ANEPPS along with Di-8-ANEPPS are classic voltage-sensitive dyes with rapid response kinetics that have been used for cardiac recordings for decades (2, 5). Although limited by sensitivity, dyes of this kind can provide excellent signal-to-noise based on brightness and photostability. Additionally, ratiometric techniques (1, 3, 5) may be employed for artifact removal such as slow bleaching or rapid movement artifacts. More recently, fluorinated dyes such as ElectroFluor530^TM (aka Di-4-AN(F)EPPTEA)  and ElectroFluor560^TM (aka Di-4-AN(F)EP(F)PTEA)  were developed  for improved signal-to-noise and these patented  dyes promise to take over from the classic dyes as the new work horses of voltage imaging.

Long wavelength dyes such as Di-4-ANBDQBS and Di-4-ANBDQPQ (4) were developed for improved sensitivity and spectral compatibility with blood infused, whole-heart preparations. Impressive research using this patented technology  shows electrical activity of the heart in a striking, highly detailed, real-time view. These experiments point to potential future clinical applications of voltage-imaging in the heart. Potentiometric Probes is working with Cytocybernetics to supply these dyes, develop novel assays for their use, and work on further improvements.