Real-time monitoring and in vivo visualization of acetylcholinesterase activity with a near-infrared fluorescent probe

Acetylcholinesterase (AChE) plays a crucial role in the activities of the nervous system, and its abnormal function can lead to the occurrence and development of neurodegenerative diseases. Hence, an effective method for real-time monitoring of AChE activity is essential. Very recently, several fluorescence sensors have been developed for the detection of AChE activity, but they are usually imaging in the visible region, relatively small Stokes shifts, or long response times, limiting their application for real-time monitoring in vivo. Inspired by that, a near-infrared (NIR) off-on probe ((E)-4-(2-(4-(dicyanomethylene)-4H-chromen-2-yl)vinyl)phenyl dimethylcarbamate, DCM-N) for AChE monitoring with high selectivity and sensitivity is developed. In the probe DCM-N, a bright near-infrared fluorescence emission at 700 nm can be triggered by AChE through the cleavage of amino ester bond in DCM-N, and the resulting fluorescence exhibits a good linear relationship with AChE activity in the range of 0.2 to 16 U/mL, with a detection limit as low as 0.06 U/mL. For real plasma sample detection, DCM-N demonstrates advantages of accurate detection and fast response compared to the traditional Ellman assay for AChE detection. Moreover, DCM-N can be used for imaging of AChE activity in live cells and tracking of AChE activity in zebrafish models, which is of great significance for medical and physiological research related to AChE. DCM-N possesses several notable features such as light-up NIR emission, fast response, large spectral shifts and strong photostability under physiological conditions. These features enable it to monitor AChE activity both in vivo and in vitro, providing a suitable tool for real-time monitoring and in vivo visualization of AChE activity.