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

Greigite magnetic nanoparticles (Fe 3 S 4 -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 H 2 O 2 during enzymatic oxidation of glucose by glucose oxidase, and the formation of a blue product from an enzyme substrate that is catalytically oxidized by H 2 O 2 in the presence of Fe 3 S 4 -MNPs. Glucose can be detected in the 2 to 100 μM concentration range, and the low detection limit is 0.16 μM. 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. Fe 3 S 4 magnetic nanoparticles (MNPs) are shown to act as peroxidase mimetics and this was used to design a glucose oxidase (GOx) based glucose assay where the H 2 O 2 formed during oxidation of glucose oxidizes tetramethylbenzidine (TMB) to give a blue product which can be quantified by photometry.