Highly selective fluorescent chemosensor with red shift for cysteine in buffer solution and its bioimage: symmetrical naphthalimide aldehyde

A new fluorescent probe 1, N-butyl-4, 5-(p-aldehyde)phenyl-1,8-naphthalimide, was designed and synthesized for the determination of the cysteine (Cys). Upon addition of Cys, the emission of 1 was enhanced with about 25 nm red-shift in the emission maximum (from 455 to 480 nm), accompanied with the fluorescent color change from blue to cyan, which was attributed to the reaction of the aldehyde groups in 1 with cysteine to form very stable thiazolidines derivative. Compound 1 was highly selective for cysteine detection without the interference of other amino acids and can be used for bioimaging of Cys.