ELISA measurement of Aβ40 and Aβ42

Serum samples were analyzed for Aβ₄₀ and Aβ₄₂ using commercial ELISA kits (Genetics Company, Schlieren, Switzerland). Serum samples were diluted in assay buffer and processed according to the manufacturer’s recommended protocols. Briefly, samples and standards were incubated in capture wells overnight at 4 °C with either a biotinylated Aβ₄₀ or an Aβ₄₂-specific antibody. After several rinses, the enzyme-conjugated detection reagent was added to the wells for 30 min. After additional rinses, wells were incubated with the chromogen solution for 30 min at room temperature and were shielded from light. After the addition of the stop solution, the wells were read for absorption at 450 nm and the Aβ concentration in the samples was calculated based on standard curves.