A ratiometric fluorescence sensor for special detection of β-galactosidase and screening of its inhibitor in complex mixtures.

β-Galactosidase (β-Gal) serves as the critical biomarker for age-related disorders, and is closely related to fruit ripening and senescence. In this study, the depletion of p-nitrophenyl-β-d-galactopyranoside (PNPG) attenuated both the Förster resonance energy transfer (FRET)-mediated quantum dots (QDs) quenching and the inner-filter effects (IFE)-induced suppression of carbon dots (CDs) fluorescence, while the accumulating p-nitrophenol (PNP) conversely amplified FRET efficiency in QDs. Consequently, the ratiometric fluorescence signal (F/F) showed a positive correlation with β-Gal activity. Under optimal experimental conditions, the method demonstrated excellent linearity in the range of 5-200 U/L R = 0.9969, with a detection limit of 0.67 U/L. The established method was successfully applied to the high-throughput and sensitive detection of β-Gal in complex matrices (such as human serum, urine, and ripe fruits). Additionally, we identified 10 traditional Chinese medicinal herbs containing β-Gal inhibitors from 20 candidates. This study could lay the foundation for the rapid, specific and high-throughput detection of β-Gal as well as for the discovery of novel β-Gal inhibitors.