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+.