A degradable NIR Ratiometric probe for HClO monitoring from cellular imaging to smart platforms

Real-time monitoring of hypochlorous acid (HClO) remains challenging due to its high reactivity, facile decomposition, and potent oxidizing nature. Herein, a near-infrared (NIR) ratiometric fluorescent probe (PICH), designed for the specific and rapid detection of HClO, is reported. PICH achieves NIR emission by extending its π-conjugation through the strategic incorporation of olefinic double bonds as molecular linkers. Crucially, the double bond serves a dual purpose, acting as the specific recognition site for HClO and enabling the PICH's degradation mechanism. Upon reaction with HClO, PICH undergoes degradation, which disrupts its extended conjugation. This results in a significant hypsochromic shift in both excitation and emission spectra, effectively moving the signal out of the NIR range. This unique response enables PICH to achieve instantaneous (< 7 s), ratiometric detection of HClO with a remarkably low detection of limit of 44.2 nM. PICH exhibits outstanding selectivity for HClO over a wide range of competing reactive oxygen species. Consequently, PICH enables precise, transient monitoring of HClO dynamics in complex biological and environmental settings. It successfully tracks both endogenous and exogenous HClO fluctuations in live cell imaging. Furthermore, integrated with a smartphone-based platform, PICH facilitates real-time quantitative measurement of HClO levels in environmental samples. This work presents a rationally designed ratiometric NIR probe for the precise, instantaneous, and selective detection of HClO, offering a powerful tool for real-time HClO monitoring across diverse applications from cellular biology to environmental science.