A FRET-based ratiometric fluorescent probe for highly selective detection of hydrogen polysulfides based on a coumarin-rhodol derivative.

In modern biology, hydrogen polysulfides (HS, n > 1) are members of reactive sulfur species (RSS), with anti-oxidation, cell protection and redox signals in tissues and organs. Therefore, it is crucial to develop a method to monitor the changes of HS level in organisms. We designed and synthesized a ratiometric fluorescent probe for highly selective detection of HS based on the fluorescence resonance energy transfer (FRET) process. In this work, a coumarin derivative was chosen as an energy donor, a rhodol derivative was used as an energy acceptor and a 2-fluoro-5-nitrobenzoate group was applied as a recognition unit for HS. In the absence of HS, the rhodol receptor existed in the non-fluorescent spirolactone state and FRET process was disabled. In the presence of HS, the closed spirolactone form was converted to a conjugated fluorescent xanthenes form to invoke the occurrence of FRET which resulted in a 77 nm red-shift of fluorescence emission from 460 nm to 537 nm. The ratio value of the fluorescence intensity between 537 nm and 460 nm (I/I) of the probe exhibited a good linear relationship toward HS in the range of 3.0 × 10-1.0 × 10 mol·L, and the detection limit was estimated to be 8.0 × 10 mol·L. In addition, the ratiometric fluorescent probe showed high specificity for HS over other biologically related species. Moreover, the probe displayed little cell toxicity and had been successfully used to the confocal imaging of HS in HepG2 cells by dual emission channels.