Peroxidase-like activity of amino-functionalized magnetic nanoparticles and their applications in immunoassay

• Surface modification does not affect the peroxidase-like activity of MNPs.
• Modified MNPs display much better thermal stability and pH tolerance than HRP.
• Modified MNPs were successfully applied in the detection of hCG.
• Modified MNPs were separation carriers and detection indicator in the immunoassay.

Amino-functionalized Fe3O4 magnetic nanoparticles with high peroxidase-like activity (MNPs–NH2) are reported in this work. The peroxidase-like activity is approximately the same as naked Fe3O4 magnetic nanoparticles (MNPs). MNPs–NH2 displayed much better thermal stability and pH tolerance than horseradish peroxidase (HRP). The optimal pH and temperature are approximately pH 4 and 40 °C, respectively. We showed that the MNPs–NH2 were successfully applied in a double-antibody sandwich “enzyme”-linked immunosorbent assay to replace of HRP, in which MNPs–NH2 were not only separation carriers, but also detection indicator.

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