Development of a selenide-based fluorescent probe for imaging hypochlorous acid in lysosomes

• A lysosome-targetable fluorescent probe for HOCl was synthesized.
• It showed a fast fluorescence response to HOCl in aqueous solution.
• The probe displayed a large fluorescence enhancement.
• Imaging of exogenous HOCl in lysosomes of living cells was achieved using fluoresce microscope.

The development of fluorescent probes for hypochlorous acid (HOCl) has received intense attention because of the biological significance of HOCl. In this work, a novel fluorescent probe based on a selenide switch for the detection of HOCl in lysosomes has been designed and synthesized on a 1,8-naphthalimide scaffold. The probe exhibited a high selectivity for HOCl over various reactive oxygen species (ROS) with a fast response and a large fluorescence enhancement in aqueous media. Confocal microscopy imaging of living cells indicated that the probe was able to accumulate in lysosomes and was successfully applied to imaging exogenous HOCl in living cells. Attempts of using Lyso-NI-Se to image HOCl in stimulated RAW264.7 cells failed, probably due to the absence of endogenous HOCl in lysosomes or the undesirable detection limit.