Fabrication of dextran-grafted magnetic polymer microspheres with low nonspecific protein adsorption as carriers for chemiluminescence immunoassays

Inhibiting the nonspecific protein adsorption on the surface of magnetic microspheres has become a pressing challenge for immunoassays. In this paper, a novel dextran-modified sandwich-type magnetic polymer microsphere was developed and demonstrated to be a promising carrier for chemiluminescence immunoassay (CLIA). Dextran-modified sandwich-type magnetic polymer microspheres (PFS-PGDN) were synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP) and ring-opening reaction of epoxy and aminodextran on the surface of magnetic P(GMA-MMA)-NH2@Fe3O4@SiO2 (PFS) microspheres. Then, carboxylated dextran-modified sandwich-type magnetic polymer microspheres (PFS-PGDC) were prepared by the surface carboxylation of the microspheres, which allowed the prepared microspheres to better couple with nucleic acids or antibodies. It is found that after grafting dextran, magnetic PFS-PGDC microspheres could significantly reduce the nonspecific protein adsorption by over 90%. The chemiluminescence immunoassay assay showed a reduction of the background value to a very low level, indicating that the magnetic spheres showed significant advantages in improving the sensitivity of the chemiluminescence assay. Moreover, the chemiluminescence sensitivity and signal values of the synthesized magnetic microspheres have reached high levels. Therefore, the magnetic microspheres synthesized here hold great promise for applications in the field of CLIA.