Two-photon fluorescent probe for lysosome-targetable hypochlorous acid detection within living cells

The design of robust tools for hypochlorous acid (HClO) detection at subcellular level is highly desired for the better understanding of its biological function in cellular signaling pathways. Herein, we report the development of a two-photon fluorescent probe (TPFP) for lysosome-targetable HClO detection through the integration of a lysosome-targetable group (aminoethyl)morpholine, two-photon fluorophore 1,8-naphthalimide and HClO capturing phenyl-thiourea together. In the presence of HClO, the thiourea moiety is oxidized to urea and thereby restores the fluorescence of 1,8-naphthalimide(at 538 nm) due to the inhibition of photo-induced electron transfer (PET) effect. As is demonstrated in the spectroscopic characterizations, the probe TPFP exhibits excellent probing performance toward HClO, including short response time (<30 s), outstanding selectivity, high photostability and low detection limit (∼5.7 nM). In addition, it is confirmed that TPFP displays promising cell-membrane permeability and high specificity toward HClO in lysosomes through the one-photon and two-photon intracellular fluorescent microscopic imaging experiments. As a consequence, this lysosome-targetable two-photon fluorescent probe provides a promising platform for HClO detection at subcellular level and would inspire the design of plummy tools for other analytes detection.