Influence of exposed magnetic nanoparticles and their application in chemiluminescence immunoassay

To a certain extent, uneven coating of nanoparticles may lead to exposure of their contents. In this work, a simulation system was established and exposed Fe 3 O 4 magnetic nanoparticles (MNPs) were used to investigate the influence of the exposed case in a chemiluminescence immunoassay. Some factors such as the concentration of MNPs, coexistence of horseradish peroxidase (HRP), different particle sizes, and various treatment methods were investigated. It was confirmed that both the bodies of nanoparticles and metallic oxides on the exposed surface have associations with the detection signal. This conclusion may provide a new way to explain the deviation emerged in a chemiluminescence immunoassay. In addition, an exposed Fe 3 O 4 MNPs based chemiluminescence immunoassay was developed to detect human chorionic gonadotropin (hCG). Carboxyl-functionalized MNPs were modified with anti-α-hCG antibody, and further used as solid-phase supports for sandwich-type immunoassay. The detection limit for hCG under optimal conditions was as low as 1.184   ng/mL with a linear response range of 2–100   ng/mL and a correlation coefficient of 0.989. The proposed method could be used for the determination of hCG in serum samples, which demonstrated their application potential in rapid and cost-effective detection of biological samples.