A turn-on two-photon fluorescent probe for detecting lysosomal hydroxyl radicals in living cells

[Display omitted] •A turn-on two-photon fluorescent probe for OH detection in lysosomes is developed.•This probe exhibits high selectivity and low detection limit.•The probe can be used for intracellular OH detection in living cells. The detection of reactive oxygen species (ROS) in biological systems and its imaging is of great importance. Among them, the hydroxyl radical (OH) stands out as one of the most reactive, playing an important role in many physiological and pathological processes. Here we report a two-photon (TP) turn-on fluorescent probe with good selectivity and sensitivity towards OH. The molecular design of this naphthalene-indoline compound enables it to accurately target lysosomes in its non-fluorescent (“off”) state, where interaction with OH gives rise to the fluorescent (“on”) state and allows for the imaging of OH generation in living mouse embryonic fibroblast (MEF) cells. The present study provides an approach for improving our understanding of the role of OH in biological processes.