A dual-signal fluorometric and colorimetric sensing platform based on gold-platinum bimetallic nanoclusters for the determination of β-galactosidase activity

Herein, a novel dual-signal sensing system for the determination of β-galactosidase (β-Gal) activity was established, which was based on a dual-emission probe assembled from gold-platinum bimetallic nanoclusters (Au–Pt NCs) and rhodamine B. Under the catalysis of β-Gal, 4-nitrophenyl β-D-galactopyranoside (PNPG) was rapidly hydrolyzed to generate p-nitrophenol (PNP), which has an obvious UV absorption peak at 400 nm. The hydrolyzed product PNP can quench the fluorescence of Au–Pt NCs effectively by inner filter effect (IFE), and PNP had no impact on the fluorescence of rhodamine B, which will change the emission intensity ratio of Au–Pt NCs and rhodamine B. Therefore, the ratiometric fluorescent and colorimetric dual-signal sensor based on Au–Pt NCs and rhodamine B was successfully constructed for sensitive detection of β-Gal activity. The linear detection range for the ratiometric fluorescence and colorimetric methods were 2.5–25 U/L and 15–55 U/L with detection limits of 1.2 U/L and 5.2 U/L, respectively. The developed assay method has been used for quantitative detection of β-Gal in spiked serum samples and showed good performance. And the detection platform has high reliability and excellent selectivity, which opens a new avenue for the further application of Au–Pt NCs in chemical sensing and biological analysis.