Antibody-functionalized magnetic nanoparticles for electrochemical immunoassay of α-1-fetoprotein in human serum

A simple and sensitive electrochemical immunoassay protocol for the detection of alpha-1-fetoprotein (AFP) has been designed based on antibody-functionalized core-shell-shell nanocomposite particles. The core-shell CoFe2O4/(3-mercaptopropyl) trimethoxysilane (CoFe2O4-MPS) was initially synthesized by covalent conjugation, then gold nanoparticles were adsorbed onto the surface of CoFe2O4-MPS via an Au-S bond, and then anti-AFP antibodies were immobilized onto the nanogold surface. With the aid of the external magnet, the biomolecules-doped magnetic nanoparticles were attached to the electrode surface. The electrochemical response was based on the modification of potential (potentiometric method) due to the interfacial change of charges as a consequence of the antigen-antibody reaction. Under optimal conditions, the immunosensor exhibited rapid response and a linear range from 0.8 to 120 ng mL(-1) AFP with a detection limit of 0.3 ng mL(-1) (S/N = 3). Moreover, the precision, reproducibility, selectivity and stability of the immunosensor were acceptable. Analytical results, obtained for the clinical serum specimen by the immunosensor, were in accordance with those assayed by the standard ELISA.