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.