Ratiometric Determination of Nitroxyl Utilizing a Novel Fluorescence Resonance Energy Transfer-Based Fluorescent Probe Based on a Coumarin-Rhodol Derivative

[Image: see text] Nitroxyl (HNO) is a member of the reactive nitrogen species, and how to detect it quickly and accurately is a challenging task. In this work, we designed and prepared a fluorescent ratiometric probe based on the fluorescence resonance energy transfer (FRET) mechanism, which can detect HNO with high selectivity. The coumarin derivative was used as an energy donor, the rhodol derivative was applied as an energy receptor, and 2-(diphenylphosphine)benzoate was utilized as the recognition group to detect nitroxyl. In the absence of HNO, the rhodol derivative exists in a non-fluorescent spironolactone state, and the FRET process is inhibited. Upon adding HNO, the closed spironolactone form is transformed into a conjugated xanthene structure and the FRET process occurs. This probe could specifically recognize nitroxyl, showing high sensitivity and selectivity. When the HNO concentration was changed from 3.0 × 10(–7) to 2.0 × 10(–5) mol·L(–1), I(543nm)/I(470nm) exhibited a satisfactory linear correlation with the concentration of HNO. A detection limit of 7.0 × 10(–8) mol·L(–1) was obtained. In addition, almost no cell toxicity had been verified for the probe. The probe had been successfully applied to the ratiometric fluorescence imaging of HNO in HepG2 cells.