Dyeing hearts deeply

With a growing inventory of light-emitting molecular tags that label specific cellular parts or that respond to specific cellular acts, biologists are visualizing ever more details about cellular anatomy and physiology. Now Guy Salama of the University of Pittsburgh and colleagues there and at Carnegie Mellon University have devised a series of structurally related dyes (example shown) that respond to the electric fields of heart muscle cells by emitting infrared light (J. Membr. Biol. 2005, 208, 125). That's important, says Alan Waggoner of CMU, because IR light penetrates tissue. In experiments using excised animal hearts, the researchers have shown that they can use the voltage-sensitive dyes to track electrical activity in cells up to a millimeter into cardiac tissue, not just in surface cells. A primary goal of the work is to develop new imaging techniques for studying how electrical excitations go awry in arrhythmic hearts and in sudden cardiac deaths.