A label-free electrochemical immunosensor for beta-amyloid detection

A label-free detection of beta-amyloid (beta A) protein using an electrochemical immunosensor fabricated via immobilizing specific anti-beta-amyloid antibodies (An-beta A-Abs) onto an interdigitated electrode of gold (IDE-Au) modified using a self-assembled monolayer (SAM) of dithiobis(succinimidyl propionate) [DTSP] is presented here. The beta A has been investigated as a potential biomarker for monitoring Alzheimer's disease (AD), permanent irreversible and progressive brain damage. Thus beta A detection at the pM level is of high significance for AD diagnostics. The IDE-Au modification and covalent immobilization of An-beta A-Abs onto electrodes were characterized by differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) as a function of electrical response variation in each step involved in sensor fabrication. The EIS studies confirmed that the developed beta A immunosensor is selective and exhibits a detection limit of 10 pM, its detection range varies from 10 pM to 100 nM, and it has a high sensitivity of 11 k Omega M-1 with a regression coefficient of 0.99. Thus, the developed sensitive and selective immunosensor with the features of the IDE-Au can be integrated with a miniaturized potentiostat (M-P) to develop a sensing system to detect beta A for point-of-care (POC) applications for the assessment and management of AD. The bio-informatics gathered from such a system could be useful to make timely therapeutic decisions.