Colorimetric sandwich immunosensor for Aβ(1-42) based on dual antibody-modified gold nanoparticles

•A newly colorimetric sandwich immunoseneor for Aβ(1-42) is constructed based on dual antibody-functionalized AuNPs.•Keeping inherent features in ELISA approaches (e.g., quantitative and specific).•Outstanding advantages of high selectivity, visualization, convenience and simplicity.•A low detection limit of 2.3 nM.

Amyloid β-peptide (Aβ) is now considered as a key predictor for preclinical diagnosis of Alzheimer's disease (AD), whose diagnosis is still hampered by the lack of early, sensitive, and convenient tools. Herein, we propose a colorimetric sandwich immunosensor for Aβ(1-42) based on dual antibody-modified gold nanoparticles. Bare AuNPs are successfully coated with N-terminal antibody of Aβ(1-42) (N-Ab(1-42)-AuNP) and C-terminal antibody of Aβ(1-42) (C-Ab(1-42)-AuNP), respectively. Subsequently, Aβ(1-42) can be simultaneously captured by the prepared AuNPs@C/N-Ab(1-42) (C-Ab(1-42)-AuNP:N-Ab(1-42)-AuNP = 1:1) owing to the specific binding of N- and C-terminal antibody with Aβ(1-42), and thus the AuNPs@C/N-Ab(1-42) are aggregated, accompanying with obvious color change from red to blue. By means of this colorimetric sandwich immunosensor system, a good linearity within a range from 7.5 nM to 350 nM is found, with a detection limit of 2.3 nM, which is equal to or better than other reported detection methods for Aβ(1-42). The newly colorimetric sandwich immunosensor system strikingly achieves specific, visual and simply detection of Aβ(1-42), and can be exploited toward the determination of other similar biomarkers related to diseases in biological or biomedical diagnosis.