Poly-Adenine Assisted Signaling Displaced Probe Ratiometric Electrochemical Aptasensor for Accurate Detection of Alzheimer's Disease Aβ Biomarkers.

Alzheimer's disease (AD) is a widely prevalent neurodegenerative condition globally, arousing significant interest in the noninvasive early detection of the disease. The concentration of amyloid β (Aβ) biomarkers in the blood is closely linked to the progression of AD, emphasizing the importance of developing a precise method for detecting these biomarkers in blood samples for early diagnosis. In this study, we developed a ratiometric electrochemical aptamer-based (EAB) biosensor for accurate detection of Aβ42 and Aβ40. The ratiometric biosensor utilizes a gold nanoparticle (AuNPs) modified electrode through an electrochemical deposition assay and a self-assembled poly-A based U-shaped structure to achieve signal changes through competitive binding of target molecules. Importantly, using the calibration of the clipping reference probe, the proposed biosensor displayed accurate detection ability for Aβ42 and Aβ40, with detection limits of 59 and 21 pM, respectively. It also has great stability and anti-interference ability in complex biological samples. Furthermore, it demonstrated satisfactory performance in detecting the Aβ peptides in a 20% FBS sample, with recoveries ranging from 96.7% to 102.2% in serum samples, and relative standard deviations (RSD) ranging from 3.3% to 8.9%. Moreover, the proposed method is expected to directly quantify the Aβ42/Aβ40 ratio by introducing a suitable reference probe, providing a potential and effective tool for the early diagnosis of AD.