Development of Probes with High Signal-to-Noise Ratios Based on the Facile Modification of Xanthene Dyes for Imaging Peroxynitrite during the Liver Ischemia/Reperfusion Process.

Xanthene-based fluorescence probes with high signal-to-noise ratios are highly useful for bioimaging. However, current strategies for improving the signal-to-noise ratios of xanthene fluorescence probes based on the replacement of oxygen group elements and extension of conjugation always require complicated modifications or time-consuming synthesis, which unfortunately goes against the original intention owing to the alteration of the parent structure and outstanding properties. Herein, a facile strategy is presented for developing a unique class of high signal-to-noise ratio probes by modifying the 2' position of a rhodol scaffold with different substituents. Systematic studies have shown that the probe named Rhod-CN-B with a strong electron-withdrawing methylene malononitrile functional group (-CH═(CN)) at the 2' position displayed a high signal-to-noise ratio and excellent photostability in aqueous solutions and could detect peroxynitrite (ONOO) without interference from other biologically active species. In addition, the excellent selectivity and sensitivity of Rhod-CN-B displayed satisfactory properties in tracking the endogenous production of ONOO in the apoptosis process of liver cells stimulated by lipopolysaccharides. Moreover, we utilized Rhod-CN-B to perform imaging of ONOO in the course of the liver ischemia/reperfusion (I/R) process, revealing that high ONOO levels were associated with aggravation of hepatocyte damage. All of the experimental data and results demonstrated that Rhod-CN-B could be a powerful tool for imaging ONOO in more physiological and pathological processes.