Ratiometric Fluorescent Probes for Detection of Intracellular Singlet Oxygen

We have developed a series of molecular probes for the fluorescent detection of singlet dioxygen (O-1(2)). The probes, based on asymmetrically substituted 1,3-diarylisobenzofurans, undergo the [2 + 4] cycloaddition reaction with O-1(2), producing ratiometric fluorescent responses. Two-photon fluorescence microscope experiments demonstrated the biological utility of the probes for the visualization of endogenous O-1(2) in macrophage cells.