A dual fluorogenic and 19F NMR probe for the detection of esterase activity

In this study, a dual-channel probe of FlE based on flavonoid derivatives is reported, which can yield “turn-on” signals of both fluorometry and 19F nuclear magnetic resonance in response to the presence of esterase. Upon the addition of esterase, FlE could convert into Fl, possessing the ESIPT effect. As a result, the fluorescence intensity was significantly enhanced and peaked at 510 nm, accompanying a change in the fluorescence of solution from nonluminous to strong green. Moreover, as determined by 19F NMR, the signal could apparently shift from δF −111.57 to −111.69 ppm. Due to the combination of these two detection approaches having good sensitivity, high selectivity, and real-time detection, FlE has been successfully applied to confocal fluorescence imaging for the detection of esterase in cells, which consistent with the 19F NMR test results in some sense.