Gold nanoparticle-loaded MoS2 nanosheets with peroxidase-like and pyranose oxidase-like activities for bio-enzyme-free visual detection of glucose, xylose and galactose

Abstract

Enzyme mimics with dual enzyme-like activities can catalyse cascade reactions with high efficiency and thus play a significant role in biochemistry since multistep cascade reactions often occur in biocatalysis. Especially, a nanozyme that simultaneously possesses peroxidase-like and pyranose oxidase (POx)-like activities is highly desired since it can be used for bio-synthetizing rare sugars and fabricating bio-enzyme-free colorimetric methods for the detection of various pyranoses. We herein prepared a novel dual-active nanozyme, which simultaneously possesses enhanced and stable peroxidase-like and POx-like activities, by loading gold nanoparticles (AuNPs) on MoS₂ nanosheets (AuNPs@MoS₂). The prepared AuNPs@MoS₂ nanozyme can catalyse various tandem reactions of pyranose oxidation and H₂O₂-mediated oxidation of TMB with high efficiency and, therefore, can be used to fabricate bio-enzyme-free colorimetric methods for the detection of various monosaccharides with a pyranyl ring, including glucose, xylose and galactose. Based on the AuNPs@MoS₂ nanozyme, we successfully developed bio-enzyme-free colorimetric methods for the detection of glucose, xylose and galactose with a visual detection limit of 0.2–0.3 mM and a spectrometry detection limit of 5.0–11 μM. The developed colorimetric glucose, xylose and galactose detection methods were successfully used to detect glucose in serum, xylose in bread and galactose in milk, respectively, with a recovery of 89–108% and a relative standard deviation (RSD, n = 5) of <5%. With enhanced peroxidase-like and POx-like activities and good stability, the developed AuNPs@MoS₂ provided a promising dual-active nanozyme for the bio-enzyme-free catalysis of various cascade reactions for the oxidation of various monosaccharides with a pyranyl ring and for further fabricating bio-enzyme-free, cost-effective and simple colorimetric sensors for the visual detection of various monosaccharides with a pyranyl ring, including glucose, xylose and galactose.