Colorimetric Detection of Antioxidants in Food Samples Using MnO₂/Graphene Quantum Dot Composites with Oxidase-like Activity

Abstract

Recently, strategies for developing colorimetric sensors relying on nanozymes for the detection of analytes of health, food, and environmental interest have gained significant importance. Herein, a rapid and sensitive colorimetric assay based on manganese dioxide/graphene quantum dot (MnO 2 /GQD) composites was developed for the detection of antioxidants in food. The composite, synthesized by a hydrothermal method, served as a nanozyme with outstanding oxidase-like catalytic activity to trigger the 3,3′,5,5′-tetramethybenzidine (TMB) chromogenic reaction. Then, an assay was performed to evaluate the reducing ability of antioxidants toward oxTMB by detecting color changes during the procedure. The colorimetric method achieved high selectivity and sensitivity toward the detection of gallic acid, tannic acid, and ascorbic acid with detection limits (S/N = 3) of 0.07, 0.28, and 0.69 μmol L −1 , respectively. Moreover, the assay was used to accurately measure and discriminate the antioxidants in real food samples, revealing its great promise for portable and rapid food analysis.

ZnO–Co3O4 Nanofibers/MXene Composite with Peroxidase-Like Activity for Ascorbic Acid Detection

“…To evaluate the peroxidase-like activity of the nanomaterials, UV–vis time-dependent kinetic studies were performed to monitor changes in the solution color associated with oxidation of the TMB chromogenic substrate. The kinetic constants were calculated using the Michaelis–Menten equation , ν = ν max [ S ] K normalm + [ S ] where ν i and ν max are the initial and maximum reaction velocities, K m is the Michaelis–Menten constant, which is associated with the affinity of the nanozyme for the substrate, and [ S ] represents the substrate concentration . The tests were carried out in acetate buffer solution, which was used to correct the final volume to 2 mL.…”

Recent Advances in Design and Application of Nanomaterials-Based Colorimetric Biosensors for Agri-food Safety Analysis

“…Facure et al established a fast and sensitive food antioxidant colorimetry method based on a MnO 2 /graphene quantum dot (MnO 2 /GQD) composite material. 66 The composite material exhibited excellent oxidase-like catalytic activity, which triggered the colorimetric reaction of TMB. The ability of antioxidants to reduce oxTMB was evaluated by the color changes during the oxidation process.…”

“…The color intensity of the paper-based test kit decreased with increasing cyanide concentration, and this test kit was successfully applied to real food samples, such as fruit juice. Facure et al established a fast and sensitive food antioxidant colorimetry method based on a MnO 2 /graphene quantum dot (MnO 2 /GQD) composite material . The composite material exhibited excellent oxidase-like catalytic activity, which triggered the colorimetric reaction of TMB.…”

Challenges and Opportunities of Using Fluorescent Metal Nanocluster-Based Colorimetric Assays in Medicine

“…Colorimetric indicators include nanoscale metallic particles, dye molecules, and transducers with selectively interacting capability in the presence of analytes which can lead to a color change. − The detection technique was used to assess the absorbance of colored compounds at a particular wavelength and visually confirms the existence of analytes . A variety of nanoplatforms are also being used for sensing applications, including carbon dots (CDs), quantum dots (QDs), gold nanoparticles (AuNPs), silver nanoparticles (AgNPs), etc. With a sensitivity below the safe limit concentrations and a regulated error range, it shows considerable promise for semiquantitative and even qualitative analysis .…”