A fluorescent chemosensor for cysteine based on naphthalimide derivative in aqueous solution

Naphthalimide derivative (compound 1) containing hydrophilic hexanoic acid group was synthesized and used to recognize cysteine (Cys) in aqueous solution. The fluorescence enhancement of 1 was attributed to the cyclization reaction of 1 with Cys by 1:1 binding stoichiometry, which has been utilized as the basis of fabrication of the Cys-sensitive fluorescent chemosensor. The comparison of this method with some other fluorescence methods for the determination of Cys indicated that the methods can be applied in aqueous solution rather than organic solution. The analytical performance characteristics of the proposed Cys-sensitive chemosensor were investigated. The chemosensor can be applied to the quantification of Cys with a linear range covering from 3.9 × 10−8 to 1.4 × 10−5 M and a detection limit of 7.8 × 10−9 M. And the chemosensor shows excellent selectivity for Cys over other amino acids. Moreover, the response of the chemosensor toward Cys is fast (response time less than 3 min). In addition, the chemosensor has been used for determination of Cys in serum samples with satisfactory results.