Immunoassay channels for α-fetoprotein based on encapsulation of biorecognition molecules into SBA-15 mesopores

A novel immunoassay channeling sensor for α-fetoprotein (AFP) was proposed by incorporating biorecognition molecules into the mesopores of well-ordered hexagonal SBA-15. As the biosensing element, alkaline phosphatase (ALP)-labeled antibody was embedded into the mesopores with the substrate of 1-naphthyl phosphate (1-NP). The encapsulated ALP-labeled antibody retained its bioactivities on catalytic hydrolysis reaction with 1-NP and immunological reaction with antigen. Ionic liquid–chitosan hybrid was chosen to increase film adherence and prevent the leakage of the immobilized molecules. The peak current responses decreased due to the increasing spatial blocking and impedance from the formation of nonconductive immunoconjugates on the surface of the electrode. The experimental parameters were optimized including the concentrations of the immobilized 1-NP and ALP-labeled antibody, and the amounts of SBA-15 and ionic liquid for the electrode modification. Under the optimized conditions, the constructed immunosensor could detect AFP in a linear range from 1.0 to 150 ng mL−1 with a detection limit of 0.8 ng mL−1. It provided an alternative strategy for the detection of antigens or other proteins by the mesoporous materials.