Dyeing Hearts Deeply

With a growing inventory of light-emitting molecular tags that label specific cellular parts or that respond to specific cellular acts such as the release of calcium or a change in a membrane???s electrical potential, biologists are visualizing ever more details about cellular anatomy and physiology.

Now Guy Salama of the University of Pittsburgh and his colleagues there and at Carnegie Mellon University have devised a series of structurally related "Pittsburgh dyes" that respond to the electric fields of heart muscle cells by emitting infrared light (J. Membr. Biol. 2005, 208, 125). That's important, says CMU chemist and biophysicist Alan Waggoner, because IR light penetrates tissue.

In experiments using excised hearts from frogs, mice, pigeons, and other animals, the researchers have shown that they can use the voltage-sensitive dyes to track electrical activity in cells as deep as 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.