A Fluorescent Probe with Zwitterionic ESIPT Feature for Ratiometric Monitoring of Peroxynitrite In Vitro and In Vivo

Peroxynitrite (ONOO^-), as a short-term reactive biological oxidant, could lead to a series of effects in various physiological and pathological processes due to its subtle concentration changes. In vivo monitoring of ONOO^- and relevant physiological processes is urgently required. Herein, we describe a novel fluorescent probe termed HBT-Fl-BnB for the ratiometric detection of ONOO^- in vitro and in vivo. The probe consists of an HBT core with Fl groups at the ortho and para positions responding to the zwitterionic excited-state intramolecular proton-transfer (zwitterionic ESIPT) process and a boronic acid pinacol ester with dual roles that block the zwitterionic ESIPT and recognize ONOO^-. Thanks to the specificity as well as low cytotoxicity, success in imaging of endogenous and exogenous ONOO^- in living cells by HBT-Fl-BnB was obtained. Additionally, the applicability of HBT-Fl-BnB to tracking the abnormal expression of ONOO^- in vivo induced by inactivated Escherichia coli was also explored. This is the first report of a fluorescent probe for ONOO^- sensing via a zwitterionic ESIPT mechanism.