Dual on-the-move electrochemical immunoassays for the simultaneous determination of amyloid-β (1-42) and Tau in Alzheimer's patient samples

Here, we report catalytic micromotors (MM)-based electrochemical immunoassays for the on-the-move dual and simultaneous determination of Amyloid-beta (A beta-42) and Tau protein (Tau) (MMA beta-42-MMTau) as relevant Alzheimer's disease biomarkers in brain tissue, cerebrospinal fluid, and plasma diagnosed samples. Combining the binding capacity of the antibody's functionalized polypyrrole (PPy) layer of MM with the self-propulsion from the PtNPs layer thanks to the decomposition of hydrogen peroxide, the approach yielded excellent detection limits (LODA beta-42=0.04 ng/mL, LODTau= 0.4 pg/mL) using low sample volumes (30 mu L) and short analysis times (15 min) to detect both biomarkers. Quantitative analysis by MMA beta-42-MMTau was carried out without any clinical sample dilution (linear ranges are between 0.1 and 5 ng/mL for A beta-42 and from 1 to 106 pg/mL in the case of Tau), highlighting the versatility of the approach to quantify A beta-42 and Tau levels at different dynamic ranges. MMA beta-42-MMTau showed superior analytical capabilities to the single molecule counting technology (SMCx) during quantitative analysis in all sample classes tested, reporting a difference in quantitative levels for both biomarkers between healthy and diseased individuals and an increase in the levels with disease progression, except in plasma samples where no relationship between biomarker levels and disease progression was found.