Development of a lysosome-targetable visible-light-excited europium(III) complex-based luminescent probe to image hypochlorous acid in living cells

Abstract Lanthanide complex-based luminescent probes have shown great utilities in detecting various analytes by time-gated luminescence imaging technology. However, few lanthanide probes are suitable for the monitoring of bioactive species in organelles. Furthermore, the common UV excitation windows of most lanthanide probes limit their application in living biological samples. In this work, a novel visible-light-excited europium(III) complex-based luminescent probe, [Eu(Lyso-CDHH)3(DPBT)], was designed and synthesized for the detection of exogenous and endogenous hypochlorous acid (HOCl) in lysosomes. The probe exhibits a wide excitation window from ultraviolet to visible region with a maximum excitation wavelength at 400 nm and a high luminescence quantum yield (41.7%). Upon reaction with HOCl, the luminescence of the probe can be quenched within 5 s and displays strong resistance to the interferences from other reactive species. The designed probe also shows high sensitivity towards HOCl with a low detection limit at micromolar concentration level. In addition, the good cell-membrane permeability and the lysosome-targetability of the probe enabled its successful application in the time-gated luminescence imaging of exogenous and endogenous HOCl in lysosomes of RAW 264.7 cells. This work will shed lights on the design of visible-light-excited and organelle-targetable lanthanide molecular probes for broader time-gated luminescence application.