▎ 摘　　要

An antioxidant (AO) amperometric technique based on guanine attached to graphene and Fe3O4 nanoparticles (NPs) magnetic materials was developed. Guanine molecules acted as an antioxidant competitor were bonded with graphene nanosheets, onto which magnetic Fe3O4 NPs were attached and the as-prepared magnetic composite can be attracted to the electrode surface by an external magnetic field. When applied with negative potentials, the dissolved oxygen was reduced to H2O2 at the electrode surface, and then reacted with the EDTA-Fe-II complex via a Fenton-like reaction to produce OH radicals. After oxidation damage by OH radicals, the electrochemical oxidation of guanine gave a decreased current. In the presence of AOs, the reactive oxygen species (ROS, e.g. OH radicals and H2O2) were scavenged by AOs and fewer guanine probe molecules were oxidized, thus inducing a higher electrochemical oxidation current of guanine. So AOs competed with the guanine probe molecules toward oxidation by ROS. The current signals of the guanine probe molecules were proportional to the concentrations of AOs. A kinetic model was proposed to quantify the ROS scavenging capacities of the AOs. Using guanine as an oxidizable probe and OH radicals and H2O2 as endogenous ROS, this kind of AO detection technique mimicks the antioxidant protection mechanism by small AO molecules in the human body.