Reasonably constructed NIR fluorescent probes based on dicyanoisophorone skeleton for imaging ONOO⁻ in living cells

Peroxynitrite (ONOO⁻), a reactive nitrogen species (RNS), engages in various cellular processes including inflammation, apoptosis, and necrosis. Therefore, the development of a powerful tool for imaging endogenous ONOO⁻ is important with regard to revealing its underlying physiological or pathological functions. In this work, we introduced dihalogen (Cl, Br, and I) at the ortho-positions of the hydroxyl group of a dicyanoisophorone skeleton to adjust its pKa to be more suitable for bio-imaging in the physiological environments with a high signal-to-noise ratio. Based on the optimized spectral results and the requirement of biocompatibility, the fluorescent probe NIR-dCl was successfully designed and fabricated for the detection of ONOO⁻. Upon the addition of ONOO⁻ in solution, an obvious NIR fluorescent signal at 680 nm was observed. Moreover, the probe NIR-dCl exhibited high selectivity for sensing ONOO⁻. Cell imaging results confirmed that probe NIR-dCl was capable of imaging exogenous and endogenous ONOO⁻ in live cells. Thus, we believe that probe NIR-dCl could be an effective tool for studying biochemical processes and ONOO⁻-related diseases.