Amyloid beta-peptide (A beta) 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 A beta((1-42)) based on dual antibody-modified gold nanoparticles. Bare AuNPs are successfully coated with N-terminal antibody of A beta((1-42))) (N-Ab((1-42))AuNP) and C-terminal antibody of A beta((1-42)) (C-Ab((1-42)))-AuNP), respectively. Subsequently, A beta(142) 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 A beta((1-42)), and thus the AuNPs@C/NAb((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 A beta((1-42)). The newly colorimetric sandwich immunosensor system strikingly achieves specific, visual and simply detection of Ail and can be exploited toward the determination of other similar biomarkers related to diseases in biological or biomedical diagnosis. (C) 2016 Published by Elsevier B.V.