A rapidly responding and highly sensitive biosensor for pH-universal detection of ONOO− and its cellular imaging

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.

A xanthene-based fluorescent probe for detection of peroxynitrite in living cells and zebrafish

Peroxynitrite (ONOO^-) is one of quite critical reactive oxygen species that acts critical roles in a number of diverse biological functions and pathological events. Notably, excessive ONOO^- will lead to sorts of diseases. Thus, monitoring of endogenous ONOO^- levels will be conducive to exploring the physiological activities and functions of ONOO^-. Here, a simple turn-on fluorescent probe named DMX is reported using CN bond as the ONOO^- recognition site and xanthene as the fluorophore. DMX possessed a good linear dependence with ONOO^- concentration (0-9 μM), highly sensitive detection (DL = 37 nM), and excellent selectivity towards ONOO^-. What is more, the biological experiments reveal that DMX is able to be utilized to track exogenous/endogenous ONOO^- employing confocal laser scanning microscopy. Visualization of ONOO^- in zebrafish was also successfully conducted, suggesting that DMX might be used to study ONOO^- roles in vivo. We believe that DMX will have potential for exploring the pivotal role of ONOO^- during all sorts of physiological and pathological activities.

Enhancing probe's sensitivity for peroxynitrite through alkoxy modification of dicyanovinylchromene

An intramolecular charge transfer (ICT)-based fluorescent probe P-ONOO^- was synthesized to detect ONOO^-. After responding to peroxynitrite, the dicyano-vinyl group of P-ONOO^- generates the aldehyde group, emitting strong green fluorescence accompanied by quenching of the yellow fluorescence. According to the calculated Fukui function, the modification of the alkoxy group can enhance the f⁺ of P-ONOO^-, which can enhance the probe's nucleophilic addition reactivity with ONOO^-. It has been experimentally verified that P-ONOO^- shows fast response (within 30 s), excellent sensitivity (the detection limit = 10.4 nM), and good selectivity towards ONOO^-. Additionally, the probe P-ONOO^- has high membrane permeability and good biocompatibility, which can image endogenous ONOO^- and exogenous ONOO^- in HeLa cells.