Real-Time Monitoring of Endogenous Cysteine Levels In Vivo by near-Infrared Turn-on Fluorescent Probe with Large Stokes Shift

TLDR

Cysteine is a key biothiol involved in protein synthesis, detoxification, metabolism, and disease, making selective near‑infrared probes for its detection in vivo highly valuable. The authors developed a selective, sensitive NIR turn‑on fluorescent probe (CP‑NIR) with a large Stokes shift to detect cysteine in vivo. The probe functions via a Michael‑addition reaction that produces a large Stokes shift and a low detection limit. The probe shifts absorption from 550 to 600 nm, emits at ~760 nm, has a 48 nM detection limit, fast response, low toxicity, good cell permeability, and successfully monitors endogenous cysteine in cells and a mouse model.

Abstract

Cysteine (Cys), as an important biothiol, plays a major role in many physiological processes like protein synthesis, detoxification and metabolism, and also is closely associated with a variety of diseases; thus the design of novel highly selective and sensitive near-infrared (NIR) fluorescent probes for Cys detection in vivo is of great significance. Herein, we report a selective and sensitive NIR turn-on fluorescent probe (CP-NIR) with large Stokes shift for detecting Cys in vivo. Upon addition of Cys to the solution of the probe, it is absorption wavelength shifts from 550 to 600 nm, accompanying with an obvious enhancement of NIR fluorescence emission centering around 760 nm. This Michael-addition reaction-based probe shows a large Stokes shift (160 nm), low detection limit (48 nM), fast response time, and low toxicity. Moreover, this novel NIR probe with good cell permeability was successfully applied to monitoring endogenous Cys in living cells and in a mouse model.