A double donor-π-acceptor type hydrogen sulfide fluorescent probe with nanomolar level sensitivity and second level response time for evaluating metformin-induced hepatotoxicity

Abstract

A dicyanomethylene-4H-pyran (DCM)-based fluorescent probe capable of hydrogen sulfide (H2S) sensing with limit of detection down to 3.89 nM, response time less than 1 s, two-photon excitation fluorescence (TPEF) feature has been developed. This probe was constructed by tethering an electron-withdrawing nitrobenzooxadiazole (NBD) moiety to the skeleton periphery of an amine-π-DCM system via ether bond. The H2S-mediated cleavage of NBD ether bond restored the electron-donating ability of amine and simultaneously generated an electron-donating phenol moiety, which enabled significantly strengthened π-delocalization over the D-π-A molecule skeleton of the reaction product and therefore turn-on fluorescence with tremendous contrast for H2S sensing with unprecedented sensitivity. The charge distribution calculation results of the probe molecule indicated the low electron density of the target carbon atom vulnerable to nucleophilic attack, which was expected to facilitate H2S-mediated nucleophilic substitution reaction and therefore contribute to the unprecedented response rate of the probe to H2S. The superior performance of such probe in terms of recognition specificity, biocompatibility and TPEF for bioimaging with satisfactory depth in mapping H2S level in physiological milieu was verified. The superior advantages of such probe regarding detection sensitivity and response rate as well as the preliminary in vitro experiment results regarding mapping the H2S level in liver organ unequivocally proclaimed its potential for reliable detection of highly elusive H2S species, a potential footprint for evaluating metformin-induced hepatotoxicity, and diagnosis of H2S-associated liver injury in practical applications.