The enzyme-linked immunosorbent assay (ELISA) is a common method used by molecular biologists for biomarker detection and quantification. And it has been considered as a sensitive and selective technique for immunoassay.

 Magnetic nano- and microparticles are widely applied in medical research including protein separation, immunoassay, magnetic resonance imaging and drug and gene targeting. Controlling the particle size, surface modification, improving the saturation magnetization and dispersity are effective method to enhance the performance of these magnetic particles in the applications.

 Researchers with Institute of Process Engineering, Chinese Academy of Sciences reported amino-functionalized Fe₃O₄ magnetic nanoparticles (MNPs-NH₂) with high peroxidase-like activity and found that the functional group modified MNPs were separation carriers and detection indicators in ELISA.

 Thermal and pH stability of MNPs-NH₂ for catalyzing one-tube tetamethylbenzidine (TMB) were investigated. Immunoassay detection of human chorionic gonadotropin (hCG) antigen by using the peroxidase-like activity of MNPs-NH₂ was performed. Enzyme activity in different temperature and pH value of MNPs-NH₂ and horseradish peroxidase (HRP) were compared as well.

 It was found that surface modification had no influence on the peroxidase-like activity of MNPs. Compared with HRP, MNPs-NH₂ showed much better thermal and pH stability. Modified MNPs were successfully used in the application of hCG detection and acted as separation carriers and detection indicators.

 The work also presented a promising biomaterial used as probes, labels and carriers in biological analytical and biomedical applications. All the results were published on the journal of colloid and interface science.