A FRET-based ratiometric fluorescent probe for sulfide detection in actual samples and imaging in Daphnia magna

Sulfide plays an important role in many important life processes, and abnormal levels of sulfide that may cause diseases. Sulfide is also essential in industrial production and food processing, and it is well concerned for environmental issues and food safety. In order to study the physiological and pathological effects of sulfide and the impact on the environment, it is still urgent to develop a convenient and effective sulfide detection technology. Here, we developed a ratiometric fluorescent probe 7-Nitro-1,2,3-benzoxoxadiazole-Acridoneacetylpiperazine (NBD-AAP) which is based on the fluorescence resonance energy transfer (FRET) between acridone and NBD fluorophores. The NBD-AAP probe could produce a ratiometric response to micromolar sulfide in buffer (pH = 7.4), exhibiting a significant enhancement in fluorescent emission ratio (F₄₂₇/F₅₅₂) and obvious visual phenomenon (orange to pink under visible light and yellow to blue under UV light). At the same time, this NBD-AAP probe also has excellent properties including high selectivity and low detection limit (0.19 μM). In addition, this probe has been successfully used for detecting the sulfide in actual samples (monosodium glutamate, beer, environmental water) and imaging in Daphnia magna. These results indicate that NBD-AAP has broad application prospects in sulfide detection and in vivo imaging studies.