Design, synthesis and application of a dual-functional fluorescent probe for reactive oxygen species and viscosity

A fluorescence probe based on cyanine fluorophore was designed and synthesized in this work, which can be used to determine viscosity and reactive oxygen species (e.g., OCl^-, ONOO^-) at different wavelengths. Under a low viscosity medium, the fluorescence quantum yield of the probe is very low; however, with the increase of the medium viscosity, the probe's emission at 571 nm is enhanced by nearly 25-fold due to the inhibition of intramolecular rotations. On the other hand, the probe shows a rapid and linear fluorescence response at 710 nm to OCl^- or ONOO^- within 1 min. The different spectral response regions of the probe permit the selective detection of both viscosity and reactive oxygen species. Furthermore, the probe is demonstrated to be cell permeable and capable of detecting the viscosity and the total amount of OCl^-/ONOO^- in living cells with the help of confocal microscope fluorescence imaging.