Smart CuS Nanoparticles as Peroxidase Mimetics for the Design of Novel Label-Free Chemiluminescent Immunoassay

In the present work, a novel label-free chemiluminescent (CL) immunoassay method was designed by employing smart CuS nanoparticles (CuSNPs) as peroxidase mimetics. The CuSNPs were synthesized through a simple coprecipitation method, and showed high catalytic activity and stability. This efficient label-free CL immunoassay could be easily achieved through a simple strategy. First, CuSNPs dispersed in chitosan were modified on the epoxy-functionalized glass slide to form a solid CL signal interface. Streptavidin was then used to functionalize CuSNPs to capture the biotinylated antibody, further producing a sensing interface. After online incubation with antigen molecules, the formed antibody-antigen complex on the biosensing substrate could prevent the diffusion channel of CL substrate toward the signal interface, and restrained the mimic enzyme-catalyzed CL reaction, finally resulting in the decrease of CL signals of the assay system. Compared to the label-based CL immunoassay, the proposed label-free assay mode is more simple, cheap and fast. Using a model analyte alpha-fetoprotein, the label-free CL immunoassay method had a linear range of 0.1-60 ng/mL and a low detection limit of 0.07 ng/mL. Moreover, the peroxidase mimetic-based label-free CL immunoassay system showed good specificity, acceptable repeatability, and good accuracy. The study provided a promising strategy for the development of highly efficient label-free CL immunoassay system.