Amperometric Aptasensor for Amyloid-β Oligomer Detection by Optimized Stem-Loop Structures with an Adjustable Detection Range

Abstract

Amyloid-β oligomers (AβO) have become representative biomarkers for early diagnosis of Alzheimer's disease. Here, we report on an aptasensor based on stem-loop probes for sensitive and specific detection of AβO by an amperometric transducer principle using alternating current voltammetry (ACV). Stem-loop probes with redox-active moieties are immobilized on a gold substrate as a receptor element. The signal transduction mechanism relies on redox ferrocene (Fc) reporting via charge transfer on a molecular recognition event involving a conformational change of the molecular beacon. The stem-loop structures were optimized by considering the aptamers' stem length, spacer, and different ferrocene terminals. In addition, the sensor assembly and signal recording including aptamer concentration and ACV frequency dependence are discussed. Using the optimized stem-loop probe (B-3′ Fc), the aptasensor showed a decrease of the Fc peak current induced by AβO binding within the broad concentration range spanning 6 orders of magnitude. Furthermore, the detection limit of the sensor can be further decreased by optimizing the ACV frequency, however at the cost of a narrowed detection range. In this work, a label-free electrochemical aptasensor is demonstrated, which facilitates the quantification of the concentration of AβO with high selectivity and subpicomolar sensitivity, which may be conducive to improving the diagnosis and pharmacology studies of Alzheimer's disease.

Advances in aptamers against Aβ and applications in Aβ detection and regulation for Alzheimer's disease

“…Mayer's group realized ultra-low concentration detection of Aβ 40 oligomers based on hairpin-based DNA aptamer probes 109 . As shown in Figure 3 C , the sensitive quantitative analysis of Aβ 40 oligomers was achieved (LOD: 2 fM) by adjusting the peak current of ferrocene by optimizing the length of the probe stem and the ferrocene end, which may help to promote the diagnosis and pathology of AD.…”

“…Adapted with permission from Ref. 109 , copyright 2019 American Chemical Society. (D) A multi-electrode array chip modified based on 3D nanostructures used for the simultaneous detection of ATP and Aβ 40 oligomers.…”

Electrochemical Biosensors Based on Micro‐fabricated Devices for Point‐of‐Care Testing: A Review

“…The combination of MEAs and biorecognition is another popular platform for POCT because they can simultaneously detect multiple targets through the high [71]. As shown in Figure 5B, this 3D nanostructured MEAs chip was sequentially modified with dual aptamer receptors for simultaneous detection of ATP and amyloid-β oligomers (AβO).…”

“…(A) Scheme of multi-well MEAs for neuro-pharmacological drug screening, reprint permission was acquired from Royal Society of Chemistry [70]. (B) 3D nanostructured MEAs chip for dual-detection of AβO and ATP, reprint permission was acquired from American Chemical Society[71]. (C) The microarray set-up immobilized with capture probes was equipped with a 4-channel flow injection system for multiplexed SPRi analysis, reprint permission was acquired from Elsevier[72].…”

Addressing Cu2+ interference for accurate aptamer-based biomarker determinations of Alzheimer’s disease

“…In recent years, several novel small molecular aptamers have been developed to recognize Aβ fibers and oligomers 6 . Specially, after Ikebukuro's team discovered an aptamer sequence which specifically recognized Aβ oligomers 7 , numerous aptamerbased methods were developed to determine Aβ oligomers with different subtypes [8][9][10][11] .…”