Mimicking Horseradish Peroxidase and NADH Peroxidase by Heterogeneous Cu²⁺-Modified Graphene Oxide Nanoparticles

Cu²⁺-ion-modified graphene oxide nanoparticles, Cu²⁺-GO NPs, act as a heterogeneous catalyst mimicking functions of horseradish peroxidase, HRP, and of NADH peroxidase. The Cu²⁺-GO NPs catalyze the oxidation of dopamine to aminochrome by H₂O₂ and catalyze the generation of chemiluminescence in the presence of luminol and H₂O₂. The Cu²⁺-GO NPs provide an active material for the chemiluminescence detection of H₂O₂ and allow the probing of the activity of H₂O₂-generating oxidases and the detection of their substrates. This is exemplified with detecting glucose by the aerobic oxidation of glucose by glucose oxidase and the Cu²⁺-GO NP-stimulated chemiluminescence intensity generated by the H₂O₂ product. Similarly, the Cu²⁺-GO NPs catalyze the H₂O₂ oxidation of NADH to the biologically active NAD⁺ cofactor. This catalytic system allows its conjugation to biocatalytic transformations involving NAD⁺-dependent enzyme, as exemplified for the alcohol dehydrogenase-catalyzed oxidation of benzyl alcohol to benzoic acid through the Cu²⁺-GO NPs-catalyzed regeneration of NAD⁺.