A novel fluorescent sensor for detection of highly reactive oxygen species, and for imaging such endogenous hROS in the mitochondria of living cells

A new dye, PTZ-Cy2, based on a hybrid cyanine-phenothiazine platform, is described. Oxidation by highly reactive oxygen species (hROS) involves attack at the thiazine sulfur atom and destruction of the pi conjugation of the cyanine moiety. Dual fluorescence emissions are enhanced dramatically at lambda(em) 470 nm and 595 nm, and PTZ-Cy2 thus serves both as an absorbance ratiometric and a fluorescent off-on sensor for detecting hROS. Moreover PTZ-Cy2 shows selectivity for hROS over other oxidants, and gives a highly sensitive response to such endogenous species within the mitochondria of living cells.