A fluorescent biosensor based on graphene quantum dots/zirconium-based metal-organic framework nanocomposite as a peroxidase mimic for cholesterol monitoring in human serum

Abstract In this study, graphene quantum dots/zirconium-based metal–organic framework (GQDs/UiO-66) nanocomposite was synthesized via a solvothermal procedure in one pot. The photocatalytic activity of the prepared GQDs/UiO-66 nanocomposite in peroxidase-like reactions was investigated using colorimetric and spectrofluorometric techniques. The photocatalytic activity of the nanocomposite in peroxidase mimetic-based fluorescence analysis of H2O2 based on H2O2-terephthalic acid reaction was considerably enhanced in comparison with its components. Owing to the fact that H2O2 could be produced as a result of enzymatic oxidation of cholesterol, and there is a linear relationship between the fluorescence intensity and cholesterol concentration, a fluorescent biosensor was developed for indirect determination of the cholesterol. In the optimal condition, the calibration plot was linear in the concentration range between 0.04 and 1.60 µmol L−1, with a detection limit of 0.01 µmol L−1. The method validation was checked by analyzing the NIST SRM 1952a-2, as a certified reference material, and the evolved technique was successfully used for cholesterol quantification in human serum samples.