Detection of Amyloid-β(1-42) Aggregation With a Nanostructured Electrochemical Sandwich Immunoassay Biosensor.

Amyloid-β(1-42) [Aβ(1-42)] oligomer accumulations are associated with physiologic alterations in the brains of individuals with Alzheimer's disease. In this study, we demonstrate that a nanostructured gold electrode with deposited gold nanoparticles, induced via electrochemical impedance spectroscopy (EIS), may be used as an Aβ(1-42) conformation biosensor for the detection of Alzheimer's disease. Monoclonal antibodies (12F4) were immobilized on self-assembled monolayers of the electrochemical sandwich immunoassay biosensor to capture Aβ(1-42) monomers and oligomers. Western blot and fluorescence microscopy analyses were performed to confirm the presence of Aβ(1-42) monomers and oligomers. EIS analysis with an equivalent circuit model was used to determine the concentrations of different Aβ(1-42) conformations in this study. We identified conformations of Aβ(1-42) monomers and Aβ(1-42) oligomers using probe antibodies (12F4) by employing EIS. R Aβ ( 1 - 42 ) indicates the sum resistance of impedance measured during Aβ(1-42) immobilization. Δ R 12 F 4 refers to the concentration of probe antibody (12F4) binding with Aβ(1-42). The concentration of Aβ(1-42) oligomer was defined as the percentage of Aβ(1-42) aggregation R 12 F 4 / R Aβ ( 1 - 42 ) . The experimental results show that the biosensor has high selectivity to differentiate Aβ(1-40) and Aβ(1-42) monomers and Aβ(1-42) oligomers and that it can detect Aβ(1-42) oligomer accurately. The linear detection range for Aβ(1-42) oligomers was between 10 pg/ml and 100 ng/ml. The limit of detection was estimated to be 113 fg/ml.