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.