A Highly Stable Graphene-Based Metal Oxide Nano Enzyme with the Peroxidase-Mimetic Activity for Equipment-Free Diagnosis of Diabetic Patients

Nanozymes are gaining attention as promising alternatives to natural enzymes due to their unique characteristics. In this study, CuO nanoparticles were decorated on three-dimensional nitrogen-doped graphene-based frameworks (CuO/3D(N)GFs) were prepared through a facile hydrothermal process. The prepared nanocomposite was characterized using XRD, EDX, FTIR, and SEM to determine its structure, composition, and morphology. The CuO/3D(N)GFs showed excellent peroxidase mimetic activity, followed Michaelis-Menten kinetics, and exhibited better kinetic parameters (Km and V-max) for H2O2 substrate than the natural enzyme, making it a superior catalyst. A rapid and facile colorimetric platform was developed to diagnose diabetes with the naked eye by coupling the activities of the nanozyme and glucose oxidase. This technique can quantitatively measure the glucose with high precision in diabetic patients, with a linear range of 1-10 mM and good sensitivity/selectivity toward glucose. The highest peroxidase-like activity of the nanozyme was observed at 30 degrees C, but it still retained over 60 % of its activity between 20-65 degrees C and showed long-term storage stability. Therefore, the CuO/3D(N)GFs nanocomposite holds promise for catalysis, biosensing, and bioanalysis applications.