A dual-responsive fluorescent probe for hypochlorous acid and copper(II): design, environmental applications, and signal transduction mechanism

Hypochlorous acid (HClO/ClO^-) and copper ions (Cu²⁺), which function as a reactive oxygen species and an essential redox regulator respectively, play critical roles in biological and environmental systems. However, their dysregulation has been associated with oxidative stress, metabolic disorders, and environmental toxicity, thus highlighting the need for precise detection methods. To address this, a novel acylhydrazone-based fluorescent probe, DPPT-HBH, was successfully developed to enable highly selective and sensitive simultaneous detection of HClO/ClO^- and Cu²⁺ in both biological systems and environmental samples. In DPPT-HBH, the hydrophobic triphenylamine moiety enabled LDs targeting, while the CN double bond provided a unique interaction site for HClO/ClO^- and the acylhydrazone structural unit (-CN-NH-CO-) functioned as the binding site for Cu²⁺. Spectroscopic characterization demonstrated that DPPT-HBH exhibited a characteristic ratiometric emission shift from 567 nm (yellow) to 519 nm (green) in the presence of HClO/ClO^-, while significant fluorescence quenching was observed at 567 nm upon Cu²⁺ binding, achieving outstanding detection limits (HClO/ClO^-: 0.41 μM, Cu²⁺: 3.60 nM). DPPT-HBH was successfully employed for the quantitative detection of HClO/ClO^- and Cu²⁺ in environmental samples. Furthermore, cell and zebrafish imaging enabled visualization of HClO/ClO^- and Cu²⁺ concentration within LDs. Notably, cell and zebrafish treatment with CuCl₂ (50 μM, 2 h) was observed to induce endogenous HClO/ClO^- generation, suggesting potential synergistic regulation between Cu²⁺ and HClO/ClO^- in LDs-associated metabolic pathways.