An optionality further amplification of an sandwich-type electrochemical immunosensor based on biotin–streptavidin–biotin strategy for detection of alpha fetoprotein

An optionality further amplification of sandwich-type electrochemical immunosensor based on Au NPs as platform and biotin-functionalized amination magnetic nanoparticle composite (B-APTES@Fe3O4) as label was designed for detection of alpha fetoprotein (AFP) in this work. The cross-shaped SA has one free biotin-binding site available for carrying a B-Ab(2), and the other three binding sites are conjugated with a 3 equimolar ratio of B-APTES@Fe3O4. Thus, further signal amplification could be achieved as SA and B-APTES@Fe3O4 are added layer by layer on the electrode successively. Of the active biotins that were modified on the surface of APTES@Fe3O4, a part of biotins are bound to the SA and the remaining biotins can be used for further connection, which can present a dendritic spread outward. Therefore, the proposed electrochemical immunosensor has wider application range than before. Under optimal conditions, the designed immunosensor exhibited a wide linear range from 1 pg mL(-1) to 10 ng mL(-1) with a low detection limit of 0.33 pg mL(-1) (S/N = 3) for HIgG. The proposed immunosensor provides a promising application for the quantitative detection of biomolecules in serum samples.