Electrochemical Immunosensors for Effective Evaluation of Amyloid-Beta Modulators on Oligomeric and Fibrillar Aggregation Processes

Abstract

A novel electrochemical immunosensor fabricated from gold compact disc electrodes was designed for rapid evaluation of aggregation processes that lead to the formation of oligomeric and fibrillar states of amyloid-beta(1-42) (Aβ(1-42)) during Alzheimer's disease. Conformation-specific antibodies were immobilized on the surface of the gold electrode using a 3,3'-dithiobis (sulfosuccinimidyl) propionate (DTSSP) linker. Surface binding events were analyzed by electrochemical impedance spectroscopy (EIS) in which the formation of an antigen-antibody complex was quantified as a function of charge transfer resistance using a [Fe(CN)6](3-/4-) redox probe. The effectiveness of novel sym-triazine-derived aggregation modulators (TAE-1, TAE-2) to reduce the population of toxic oligomers was evaluated. Aβ fibril formation was validated by thioflavin T (ThT) fluorescence, whereas oligomer formation was investigated by MALDI. Antigen detection by EIS was further supported by immuno dot blot assays for oligomeric and fibrillar components. Docking simulations of the aggregation modulators TAE-1 and TAE-2 with Aβ(1-42) fibrils performed using Autodock Vina suggest a mechanism for the improved aggregation inhibition observed for TAE-2. The results demonstrate the utility and convenience of impedance immunosensing as an analytical tool for rapid and comprehensive evaluation of effective Aβ aggregation modulating agents.

Detection of Aβ Monomers and Oligomers: Early Diagnosis of Alzheimer's Disease

“…[76] Anti-fibril and anti-oligomer antibodies were covalently attached on separate electrodes. EIS wasu sed to analyze the binding of the antigen-antibodyb ym easuring the charge-transfer resistance of a[ Fe(CN) 6 ] 3À/4À redox probe.…”

A sensitive and selective electrochemical biosensor for the determination of beta-amyloid oligomer by inhibiting the peptide-triggered in situ assembly of silver nanoparticles

“…22,23 Therefore, the direct detection of Aβ oligomer level would be more reliable for AD diagnosis than assay of its monomer. 24,25 Recently, a few novel biosensors have been developed for the detection of Aβ oligomer, including electrochemistry, [26][27][28][29] surface plasma resonance (SPR), 30 localized surface plasmon resonance (LSPR), 24,31 fluorescence, 32,33 nuclear magnetic resonance, 34 and surface-enhanced Raman spectroscopy. 35 These methods are feasible, but they require the use of special instruments and/or relatively expensive and variable antibodies for the capture and recognition of Aβ oligomer.…”

β-Amyloid Biomarker Detection for Alzheimer’s Disease

“…The AuNPs were electrodeposited on the surface of the electrode using CV, since this technique gave better results. Like other studies, this is another example of the use of self-assembled monolayers (SAMs) to develop biosensors [18]. The variation between the second and third methods is the use of protein G (PrG).…”

“…There was a considerable difference among the layers, which indicated the changes in the kinetics of electron transfer, using CV, and charge transfer resistance, using EIS (Fig. 2) [18].…”