Biomolecule-doped organic/inorganic hybrid nanocomposite film for label-free electrochemical immunoassay of α-1-fetoprotein

A new electrochemical immunosensor for the detection of alpha-1-feroprotien (AFP) was developed based on AFP antibody (anti-AFP)-functionalized organic/inorganic hybrid nanocomposite membrane. To fabricate such a hybrid composite membrane, 3,4,9,10-perylenetetracarboxylic acid-bound thionine molecules (PTCTH) were initially doped into titania colloids (TiO2), and then gold nanoparticles and anti-AFP were immobilized onto the composite film in turn. Comparison with the electrode fabricated only with thionine not 3,4,9,10-peryleneteti-acarboxylic acid, the iminunosensor with PTCTH exhibited high sensitivity and fast electron transfer. The presence of gold nanoparticles provided a good microenvironment for the immobilization of biomolecules, enhanced the surface coverage of protein, and improved the sensitivity of the immunosensor. The modified process was characterized by scanning electron microscope (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The surface topography of the membrane was investigated by scanning electron microscopy (SEM). Under optimal conditions, the proposed immunosensor exhibited a wide linear range from 2.5 to 200.0 ng/mL towards AFP with a detection limit of 0.5 ng/mL (S/N= 3). The stability, reproducibility and precision of the immunosensor were acceptable. Comparison with the conventional enzyme-linked immunosorbent assay (ELISA), the present method did not require more labeled procedures and washing steps. Significantly, the detection methodology provides a promising approach for other proteins or biosecurities.