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

Amyloid-beta(1-42) [A beta(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 A beta(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 A beta(1-42) monomers and oligomers. Western blot and fluorescence microscopy analyses were performed to confirm the presence of A beta(1-42) monomers and oligomers. EIS analysis with an equivalent circuit model was used to determine the concentrations of different A beta(1-42) conformations in this study. We identified conformations of A beta(1-42) monomers and A beta(1-42) oligomers using probe antibodies (12F4) by employing EIS. R A beta ( 1 - 42 ) indicates the sum resistance of impedance measured during A beta(1-42) immobilization. delta R-12F4 refers to the concentration of probe antibody (12F4) binding with A beta(1-42). The concentration of A beta(1-42) oligomer was defined as the percentage of A beta(1-42) aggregation R12F4/RA beta(1-42) . The experimental results show that the biosensor has high selectivity to differentiate A beta(1-40) and A beta(1-42) monomers and A beta(1-42) oligomers and that it can detect A beta(1-42) oligomer accurately. The linear detection range for A beta(1-42) oligomers was between 10 pg/ml and 100 ng/ml. The limit of detection was estimated to be 113 fg/ml.

Automated summary

This study demonstrates that a nanostructured gold electrode with deposited gold nanoparticles induced via electrochemical impedance spectroscopy (EIS) can be used as a conformation biosensor for the detection of Amyloid-beta(1-42) (A beta(1-42)) oligomers associated with Alzheimer's disease. The concentration of different A beta(1-42) conformations can be determined using EIS analysis with an equivalent circuit model. Probe antibodies (12F4) are used to identify the conformations of A beta(1-42) monomers and oligomers.