Alzheimer's disease: Development of a sensitive label-free electrochemical immunosensor for detection of amyloid beta peptide

Abstract

In this work, a highly sensitive label-free immunosensor for detection of the main biomarker ofAlzheimer's disease (AD), amyloid beta 1-42 (A (1-42)), is presented. A gold electrode was modifiedwith a mercaptopropionic acid (MPA) self-assembled monolayer, electrodeposited gold nanoparticles(AuNPs) and a monoclonal antibody mAb DE2B4 to recognize A; all the relevant experimental variableswere optimized. Antibodies were functionalized through chemical modification (thiolation) to promotethe antibody immobilization on the AuNPs surface with proper orientation which enabled the directdetection of A(1-42). Scanning electron microscopy, square-wave voltammetry and electrochemicalimpedance spectroscopy were used to characterize the construction of the biosensor. Using the proposed immunosensor, A(1-42) was specifically detected within the linear range of 10-1000 pg mL−1with a 5.2 pg mL−1 and 17.4 pg mL−1 detection and quantification limit, respectively; recovery values forthe tested spiking levels ranged from 90.3 to 93.6%. The immunosensor enables rapid, accurate, precise,reproducible and highly sensitive detection (14.6%reduction mL pg−1) of A with low-cost and opens thepossibilities for diagnostic ex vivo applications and research-based in vivo studies.