A double-locked and neutrophil elastase/hypochlorite activated probe for accurate bioimaging of osteoarthritis

In osteoarthritis, hypochlorous acid (HClO)—a critical biomarker of inflammation—and neutrophil elastase (NE)—a key mediator of inflammatory responses—undergo significant changes. Fluorescent probes, which offer high sensitivity and real-time visualization, have been widely employed for osteoarthritis imaging. However, most existing probes are designed to detect only a single biomarker, which can lead to false-positive signals in complex biological environments. In contrast, dual-locked fluorescent probes, which require activation by two distinct biomarkers, offer improved specificity and reliability. These probes are particularly advantageous for multiplexed detection in arthritis-related imaging. To date, no dual-responsive fluorescent probe targeting both HClO and NE has been reported. In this study, we introduce Cou-HN, a dual-locked fluorescent probe that exhibits a significant fluorescence enhancement at 470 nm only when both HClO and NE are present simultaneously. Neither HClO nor NE alone is sufficient to trigger a notable fluorescence response. This dual-activation strategy provides Cou-HN with superior imaging accuracy compared to single-locked probes. Both in vitro and in vivo experiments confirm its excellent performance, highlighting its promise for more precise diagnosis and monitoring of osteoarthritis.