A novel lipid droplets-targeting ratiometric fluorescence probe for hypochlorous acid in living cells

Lipid droplets were found to be involved in many organism activities. Here, a lipid droplets-targeted near-infrared fluorescence probe (named XHZ) for ratiometric detection of endogenous hypochlorous acid/hypochlorite (HClO/ClO^-) in living cells was developed, which was constructed by a coumarin moiety and a malononitrile derivative. XHZ could detect HClO/ClO^- with high selectivity and sensitivity in a ratiometric manner based on FRET (Förster Resonance Energy Transfer) mechanism. The two well-resolved emission (470/672 nm) bands could ensure accurate detection of HClO/ClO^- in vitro as well as in vivo. XHZ was successfully used for ratiometric fluorescence imaging of exogenous and endogenous HClO/ClO^- in RAW264.7 cells. A good linear relationship between the fluorescence intensity ratios of the two emissions and HClO/ClO^- concentrations from 0 to 40 μM was obtained. Importantly, XHZ could localize mainly in lipid droplets of RAW264.7 cells. To the best of our knowledge, XHZ is the first lipid droplets-targeted ratiometric fluorescence probe for HClO/ClO^-.