A sandwich-type electrochemical immunosensor based on the biotin- streptavidin-biotin structure for detection of human immunoglobulin G

A sandwich-type immunosensor is designed and fabricated to detect the human immunoglobulin G (HIgG) using polyaniline and tin dioxide functionalized graphene (GS-SnO₂-PAN) as the platform and biotin-functionalized amination magnetic nanoparticles composite (B-Fe₃O₄@APTES) as the label. GS-SnO₂-PAN is used as the sensing agent to capture the primary anti-HIgG (Ab₁) and SnO₂ reduces the stack of GS. The B-Fe₃O₄@APTES with a large surface area and excellent biocompatibility captures second antibody (Ab₂) efficiently based on the highly selective recognition of streptavidin to biotinylated antibody. The B-Fe₃O₄@APTES has better electro-catalytic activity in the reduction of hydrogen peroxide (H₂O₂) and the “biotin-streptavidin-biotin” (B-SA-B) strategy leads to signal amplification. Under optimal conditions, the immunosensor has a wide sensitivity range from 1 pg/L to 10 ng/L and low detection limit of 0.33 pg/L (S/N = 3) for HIgG. The immunosensor has high sensitivity, fast assay rate, as well as good reproducibility, specificity, and stability especially in the quantitative detection of biomolecules in serum samples.