Quantum dots-based sandwich immunoassay for sensitive detection of Alzheimer's disease-related Aβ.

Amyloid-beta peptide 1-42 (Aβ) is known as a component of amyloid plaques in association with Alzheimer's disease. Herein, we developed a reliable and remarkably sensitive sandwich immunoassay to detect the Aβ using quantum dots (QDs) as fluorescent label. In the presence of Aβ, the biotinylated Anti-beta Amyloid 1-16 (N-Ab) recognized the target and formed C-Ab-Aβ-N-Ab sandwich immunocomplexes. Then Streptavidin-QDs conjugated to biotinylated N-Ab and the concentration of Aβ was determined by detecting the fluorescence intensity in the supernatant. This method is faster and more efficient than the previous approach we reported. It also has reasonable sensitivity and selectivity. Under the optimized conditions, the linear range is 5.0 to 100 pM (0.023-0.45 ng/mL) and the detection limit is 1.7 pM (7.6 pg/ mL). In addition, this method has been successfully applied to detect the Aβ in human cerebrospinal fluid sample.