Molecular imaging of hydrogen peroxide produced for cell signaling

Hydrogen peroxide ( H2O2) is emerging as a newly recognized messenger in cellular signal transduction(1,2). However, a substantial challenge in elucidating its diverse roles in complex biological environments is the lack of methods for probing this reactive oxygen metabolite in living systems with molecular specificity. Here we report the synthesis and application of Peroxy Green 1 ( PG1) and Peroxy Crimson 1 ( PC1), two new fluorescent probes that show high selectivity for H2O2 and are capable of visualizing endogenous H2O2 produced in living cells by growth factor stimulation, including the first direct imaging of peroxide produced for brain cell signaling. The combined features of reactive oxygen species selectivity, sensitivity to signaling levels of H2O2, and live- cell compatibility presage many new opportunities for PG1, PC1 and related synthetic reagents for exploring the physiological roles of H2O2 in living systems with molecular imaging.