A pH-Gated Fluorescent Probe for Visualizing Hypochlorous Acid: From Pyroptosis to Tumor Imaging

Precise visualization of hypochlorous acid (HOCl) in vivo is limited by tissue autofluorescence and nonspecific activation. Addressing these limitations requires dual-locked logic-driven molecular tools that integrate near-infrared (NIR) emission with stringent signal gating. As a key indicator of both physiological regulation and pathological dysfunction, pH provides an important cue for disease detection. Herein, we reported a pH-gated dual-locked NIR fluorescent probe, Ac-HEP, constructed on an acridine scaffold and functionalized with pH-responsive piperazine moieties for the selective detection of HOCl through the dual-locked fluorescence-activation strategy. Unlike most tandem dual-locked probes, Ac-HEP emitted fluorescence immediately upon activation in an acidic environment, which significantly enhanced the specificity of HOCl recognition. The ability of Ac-HEP to detect pathological HOCl was verified by imaging a pyroptosis model and real-time monitoring of HOCl in an inflammation zebrafish model. Notably, Ac-HEP achieved high contrast tumor diagnosis in live mice, offering a robust tool for spatiotemporal analysis of oxidative stress. Therefore, this pH-gated dual-locked fluorescent probe capable of detecting HOCl in different pathological conditions provides a new strategy for disease diagnosis.