Flow-injection electrochemical immunosensor for the detection of human IgG based on glucose oxidase-derivated biomimetic interface

A newly flow-through electrochemical immunosensor for monitoring IgG in human serum has been developed by using core-shell SiO₂/Au nanocomposites and poly(amidoamine) G4 dendrimer as matrices. The ferrocenecarboaldehyde-labeled anti-IgG biomolecules were initially chemisorbed onto the nanoparticle surface, and then glucose oxidase (GOx), as a blocking reagent instead of bovine serum albumin (BSA), was backfilled onto the modified surface. The formation of the antibody-antigen complex by a simple one-step immunoreaction between the immobilized anti-IgG and IgG in sample solution introduced a barrier of direct electrical communication between the immobilized GOx and the base surface, and decreased the immobilized GOx toward the catalytic oxidation of glucose. The performance and factors influencing the performance of the immunosensor were evaluated. Under optimal conditions, the linear range of the developed immunosensor by using GOx as enhancer was from 5.0 × 10^-6 to 9.6 × 10^-4 mol/L with a detection limit of 8.0 × 10^-7 mol/L IgG (at 3δ), while the detection limit by using BSA was 1.5 × 10^-5 mol/L IgG (at 3δ) with the linear range from 3.5 × 10^-5 to 1.2 × 10^-3 mol/L. The selectivity, reproducibility and stability of the proposed immunosensor were acceptable. The IgG contents in 37 human serum samples obtained by the proposed method are identical with the data of clinical laboratory.