Ultrasensitive and selective fluorescent sensor for cysteine and application to drug analysis and bioimaging.

A fluorescent sensor based on coumarin-maleimide conjugate was developed for efficient discrimination of Cys from Hcy and GSH in both organic and aqueous solution. Addition of Cys to the non-fluorescent sensor solution in DMF induced bright blue fluorescence and enhanced the fluorescence intensity by 320-fold while other amino acids and biothiols (Gly, Hcy, GSH, Glu, Val, Tyr, Arg, Trp, Lys, His, Leu, Phe, Asp and Met) did not bring about remarked change. The sensor responds to Cys extremely rapidly. If Cys was added to the sensor solution, the fluorescence intensity increased by 170-fold immediately and attained the maximum value in 5 min. A linear relationship was observed between Cys concentration within 2–20 μM and the fluorescence intensity of the sensor solution. The detection limit of the sensor toward Cys is as low as 4.7 nM. The sensor is also effective for specific detection of Cys in aqueous (DMF/H 2 O = 9:1, v/v) solution. Practical application of the sensor to drug analysis and bioimaging of living Hela cells has been verified. Possible sensing mechanism of the sensor toward Cys has been proposed. A coumarin-maleimide conjugate was synthesized for fluorescence turn-on discriminating Cys from Hcy and GSH in both organic and aqueous media. The sensor is superior in respect of its low LOD (4.7 nM), rapid response (several sec‒5 min), extraordinary fluorescence enhancement (320-fold), and facile synthesis and is applicable in drug analysis and bioimaging of living cells. [Display omitted] • A coumarin-maleimide conjugate-based fluorescent sensor was synthesized facilely. • The sensor can discriminate Cys from Hcy and GSH in both organic and aqueous media. • The sensor shows low LOD of 4.7 nM and rapid response (less than 5 min) in DMF. • Addition of Cys induces fluorescence enhancement by 320-fold in DMF. • The sensor is applicable in drug analysis and bioimaging of living cells. [ABSTRACT FROM AUTHOR]