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-SnO 2 -PAN) as the platform and biotin-functionalized amination magnetic nanoparticles composite (B-Fe 3 O 4 @APTES) as the label. GS-SnO 2 -PAN is used as the sensing agent to capture the primary anti-HIgG (Ab 1 ) and SnO 2 reduces the stack of GS. The B-Fe 3 O 4 @APTES with a large surface area and excellent biocompatibility captures second antibody (Ab 2 ) efficiently based on the highly selective recognition of streptavidin to biotinylated antibody. The B-Fe 3 O 4 @APTES has better electro-catalytic activity in the reduction of hydrogen peroxide (H 2 O 2 ) 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.