Selective Detection of Sulfide in Human Lung Cancer Cells with blue-fluorescence “ON-OFF-ON” Benzimidazole-based Chemosensor Ensemble
A completely water-soluble, high quantum yield blue-fluorescent benzimidazole derivative (AQ), containing a rigid benzimidazole-thiophene structure, was synthesized. Among 21 metal ions, the fluorescence of AQ was selectively turned off by Cu2+ to form an AQ-Cu2+ ensemble. Thereby, the fluorescence of AQ-Cu2+ ensemble was turned on by sulfide (S2–) with high selectivity and sensitivity in pure water solution. By compasion to AQ-Ag+ and AQ-Hg2+ ensembles, AQ-Cu2+ was the only ensemble that capable for the detection of sulfide anion. Also, the fluorescence intensity of AQ was linearly proportional to the concentration of Cu2+ and S2–. Both Cu2+ and S2– were detected within a minute in vitro. Moreover, AQ also worked best in the range of pH 5–10 and had a limit of detection of 50 nM and 354 nM for Cu2+ and S2– respectively. It was employed for the detection of sulfide in human lung cancer A549 cells with low cytotoxicity.