Low-fouling and highly sensitive fluorescence immunoassay of protein in serum based on the antifouling magnetic beads

Aim: A low-fouling and highly sensitive fluorescence immunoassay for protein detection in serum was proposed, and IgG was used as a model protein. Materials & methods: SH-PEG-NH2 serving as antifouling coating was conjugated with carboxyl Fe3O4 nanoparticles, and then, the thiol groups were conjugated with antibody via the covalent binding. IgG was captured through magnetic immunoreaction. Highly fluorescent quantum dots modified with streptavidin (SA-QDs) were united with biotin modified IgG antibody to form the sandwich structure. Results & conclusion: The fluorescence immunoassay was able to detect IgG with a detection limit of 3.89 ng/ml in buffer and 5.0 ng/ml in serum with satisfying selectivity and acceptable reproducibility, which demonstrated its potential application in quantitative analysis of real patient serum samples.