Dual-Channel Recognition of Human Serum Albumin and Glutathione by Fluorescent Probes with Site-Dependent Responsive Features

Design of chemical probes with high specificity and responses are particularly intriguing. In this work, a fluorescent probe (M–OH–SO3) with dual-channel spectral responses toward human serum albumin (HSA) is presented. By employing dinitrobenzenesulfonate as a recognition site as well as a fluorescence quencher, probe M–OH–SO3 displayed weak fluorescence, which, nevertheless, exhibits extensive yellow (575 nm) and red (660 nm) fluorescence emissions toward HSA under excitations at 400 and 500 nm, respectively. Interestingly, M–OH–SO3 displayed the best performance toward HSA with distinctly higher selectivity than that of its counterparts M–SO3, M–H–SO3, and M–F–SO3, which were prepared simply by modulating the functional group at the ortho position of the dicyanoisophorone core. Molecular docking results revealed that M–OH–SO3 possesses the lowest binding energy among the tested derivatives and accordingly the strongest binding affinity. Probe M–OH–SO3 showed a good linear relationship toward HSA in a range of 0.5–18 μM with a limit of detection of 35 nM. Cell imaging results demonstrated that probe M–OH–SO3 could visualize the variation HSA levels in hepatocarcinoma cells. In addition, probe M–OH–SO3 could also be employed for the recognition of glutathione through the cleavage of the dinitrobenzenesulfonate group along with an enhancement of emission at 575 nm. The site-dependent properties inspired a novel paradigm for design of fluorescent probes with optimized selectivity and responses.