A sensitive colorimetric assay for cholesterol based on the peroxidase-like activity of MoS2 nanosheets

The authors describe a colorimetric method for the determination of cholesterol in human serum. Cholesterol is enzymatically oxidized by oxygen in the presence of cholesterol oxidase (ChOx) to produce 4-cholestene-3-one and hydrogen peroxide (H 2 O 2 ). Due to the peroxidase-like activity of MoS 2 nanosheets, H 2 O 2 can oxidize the chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) to give a blue product. The increase in the absorbance of the acidic oxTMB solution at 450 nm is used for quantification of cholesterol. Under the optimal conditions, the increase in absorbance is proportional to the concentration of cholesterol in the range from 2 to 200 μmol⋅L −1 , and the limit of detection is 0.76 μmol⋅L −1 . The color change from pale yellow to blue color can also be detected visually for cholesterol concentrations as low as 20 μmol⋅L −1 . Such an enzyme mimetic-based assay possesses advantages over enzyme-based assays in terms of costs, stability against denaturation, and protease digestion. The assay was applied to the determination of free cholesterol and of total cholesterol (after hydrolysis using an esterase) in spiked human serum, and it gave satisfactory recoveries. Graphical abstract Schematic presentation of the colorimetric assay of cholesterol. Cholesterol is oxidized by the catalysis of cholesterol oxidase to produce 4-cholestene-3-one and hydrogen peroxide (H 2 O 2 ) which oxidizes the substrate 3,3′,5,5′-tetramethylbenzidine (TMB) to produce a blue product (oxTMB) due to the pseudo-enzymatic action of MoS 2 nanosheets.