A facile near-infrared xanthene fluorescence probe for visualizing of hypochlorous acid in vitro and in vivo.

Background: Hypochlorous acid (HClO) is an important biomarker for inflammation, cardiovascular disease, and even cancer. It is of great significance to accurately monitor and quantitatively analyze the fluctuations of HClO to better understand their physiological functions. Traditional HClO detection methods such as high-performance liquid chromatography (HPLC), and mass spectrometry are preferred, but are costly and unsuitable in vivo. Near-infrared (NIR) fluorescence imaging has the advantages of high sensitivity, high temporal and spatial resolutions, minimal autofluorescence, and deep tissue penetration, which facilitates its application in biological systems. Therefore, the development of sensitivity and simple NIR fluorescence monitoring HClO methods in vivo and in vitro is essential and desirable.

Results: Herein, we present a NIR probe NOF3 by integrating the rhodamine scaffold and HClO-triggered moiety for the real-time detection of HClO in vitro and in vivo. NOF3 reacts with the HClO and releases the NOF-OH fluorophore of emitted signals at 730 nm, which is in the NIR region. The designed probe detected concentrations of HClO ranging from 0 to 17 μM with a low detection limit of 0.146 μM, presenting excellent sensitivity and selectivity toward HClO over other species. NOF3 manifests significantly turn-on NIR fluorescent signals in response to HClO concentration, which makes it favorable for monitoring dynamic HClO distribution in vivo. We exemplify NOF3 for the tracking of endogenously overexpressed HClO distribution in RAW 264.7 cells, and further realize real-time in vivo bioimaging of HClO activity in inflammation mice.

Significance: The facile NIR NOF3 probe was successfully applied to visualize endogenous and exogenous HClO in living cells and mice. This study provides not only an effective tool for spatial and temporal resolution HClO bioimaging in vivo but also possesses great potential for use in future research on HClO-related biology and pathology.