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.