Construction of a dual "off-on" near-infrared fluorescent probe for bioimaging of HClO in rheumatoid arthritis.

Hypochlorous acid (HClO) serves as a critical biomarker in inflammatory diseases such as rheumatoid arthritis (RA), and its real-time imaging is essential for understanding its biological functions. In this study, we designed and synthesized a novel probe, RHMB, which ingeniously integrates rhodamine B and methylene blue fluorophores with HClO-specific responsive moieties into a single molecular framework. Upon exposure to HClO, RHMB exhibited significant dual-channel fluorescence enhancement characterized by high sensitivity (LODs of 2.55 nM and 14.08 nM), excellent selectivity, and rapid response time (within 5 s). Notably, RHMB enabled reliable imaging of both exogenous and endogenous HClO in living cells and in zebrafish, employing a unique duplex-imaging turn-on approach that highlighted its adaptability across various biological contexts. Furthermore, RHMB effectively monitored HClO fluctuations in an RA mouse model and assessed the therapeutic efficacy of diclofenac (Dic) in alleviating RA symptoms. These findings underscore the potential of RHMB as an invaluable tool for elucidating the biological roles of HClO in various diseases.