A fluorescent probe for discrimination of cysteine/homocysteine, glutathione and hydrogen polysulfides

Abstract

Biothiols of cysteine (Cys), homocysteine (Hcy), glutathione (GSH) and hydrogen polysulfides (H2Sn, n > 1) play vital roles in physiological and pathological processes. In this manuscript, a fluorescent probe (compound 1) for simultaneous detection and discrimination of Cys/Hcy, GSH and H2Sn was developed, employing fluorophore of 1-(benzo[d]thiazol-2-yl)naphthalen-2-oxy linked with 7-nitrobenzo-2-oxa-1,3-diazole (NBD) as a response unit and a quencher. Compound 1 exhibited different ratiometric colorimetric responses toward GSH at 430 nm and 375 nm from Cys/Hcy at 480 nm and 375 nm, while it displayed a different colorimetric response at 561 nm toward H2Sn. Meanwhile it could act as a naked-eye probe toward GSH, Cys/Hcy and H2Sn with corresponding solution color of light yellow, orange and purple, respectively. Upon excitation at 370 nm, compound 1 responded to all these biothiols with 'turn-on' blue fluorescence, whereas upon excitation at 470 nm, it could respond to Cys/Hcy with 'turn-on' green fluorescence. Data of mass spectra, lifetimes and 1H NMR spectra interpreted the aromatic nucleophilic substitutions of compound 1 by GSH, Cys/Hcy and H2Sn to produce fluorophore1-(benzo[d]thiazol-2-yl)naphthalen-2-ol (compound 2) and corresponding NBD derivatives which could be discriminated through their absorption and fluorescence signals as well as solution colors. Furthermore, compound 1 was applied to image Cys/Hcy and H2Sn/GSH in 786-O cells.