Rational design of a far-red fluorescent probe for endogenous biothiol imbalance induced by hydrogen peroxide in living cells and mice.

• The article reports an ultrafast far-red fluorescent probe (Cou-DNBS) for biothiols with a large Stokes shift of 131 nm. • The probe was constructed by fusing an additional benzene ring. • The probe showed ultrafast response to biothiols, emitting a strong red fluorescence at 617 nm on excitation at 480 nm. • The probe was successfully employed to visualize biothiol fluctuations in living cells damaged by oxidative stress and mice. Intracellular biothiols are correlated with many diseases such as nerve disorder and Parkinson's disease likely due to a redox imbalance. In this work, we designed an ultrafast fluorescent probe (Cou-DNBS) for biothiols with a large Stokes shift (131 nm). The probe was constructed through linking the 2,4-dinitrobenzenesulfonyl moiety as the specially recognizing biothiols site to an iminocoumarin fluorophore Cou-NH obtained by fusing an additional benzene ring. The presence of biothiols could ultrafast perform a significant fluorescence emission at 617 nm upon the excitation of 480 with the low limits of detection (2.5 nM for Cys, 1.7 nM for Hcy and 0.84 nM for GSH). HRMS spectra as well as theoretical calculations further evidenced the rationale of recognition mechanism. Furthermore, the probe can successfully visualize endogenous biothiol recovery in living cells damaged by H 2 O 2. [ABSTRACT FROM AUTHOR]