Magnetic Fe3S4 nanoparticles with peroxidase-like activity, and their use in a photometric enzymatic glucose assay

Greigite magnetic nanoparticles (Fe3S4-MNPs) were prepared and reveal a peroxidase-like activity. Kinetic studies revealed a pseudo-enzymatic activity that is much higher than that of other magnetic nanomaterial-based enzyme mimetics. This finding was exploited to design a photometric enzymatic glucose assay based on the formation of H2O2 during enzymatic oxidation of glucose by glucose oxidase, and the formation of a blue product from an enzyme substrate that is catalytically oxidized by H2O2 in the presence of Fe3S4-MNPs. Glucose can be detected in the 2 to 100 mu M concentration range, and the low detection limit is 0.16 mu M. The method was applied to quantify glucose in human serum. In our perception, this enzyme mimetic has a large potential in that it may be used in other oxidase based assays, but also in ELISAs.