Dot-blot sandwich immunoassay with silver signal enhancement for simple amyloid beta protein fragment 1-42 detection

Amyloid beta 1-42 (A 1-42 ) is a key pathophysiological hallmark of Alzheimer's disease (AD). Changes in biofluids of A have been associated with AD risk. Herein, a dot-blot sandwich immunoassay was developed for simple detection of the A 1-42 using gold nanoparticles as signal label. The results were easily observed by naked eye, and an image processing program provided semi-quantitation. Furthermore, addition of silver enhancer to the assay further improved sensitivity of the measurement. The proposed assay for A 1-42 had a linear range of 1-200 g/ml, with a detection limit of 1 g/ml and 0.3 g/ml by naked eye and calculation, respectively. Performance of the developed assay was assessed in analyses of spiked plasma samples. The recoveries of A 1-42 were in the range of 112-158%, indicating that the developed assay is practical and reliable. The proposed method provides a low cost and simple assay for A 1-42 measurement.