Gold nanoparticles-modulated ECL/PEC aptasensor for the dual-mode detection of Alzheimer's disease biomarker.

A dual-mode electrochemiluminescent/photoelectrochemical (ECL/PEC) aptasensor modulated by optical and catalytic properties of gold nanoparticles (Au NPs) is constructed to determine soluble amyloid β oligomer (AβO), a critical Alzheimer’s disease (AD) biomarker. In this system, CdS quantum dots (QDs) are integrated onto an indium tin oxide electrode (ITO), acting as ECL emission source and PEC substrates. The developed sensing system enables signal transduction by exploiting the robust AβO binding ability of the developed aptamer and magnetic isolation as an enrichment strategy. The resultant AβO-dependent T strands can trigger the toehold-mediated strand displacement (TMSD) reaction, consequently enabling the assembly of copious P-Au NPs strands. By the modulation of localized surface plasmon resonance (LSPR) and oxidase-mimic performance of Au NPs on CdS QDs, the boosting ECL signal and quenching PEC response are both observed. Based on the above merits, the aptasensor can successfully determine the AβO level in a linear range spanning from 10 fM to 10 nM, with detection limits as low as 3.1 fM (ECL mode) and 3.3 fM (PEC mode). Furthermore, the applicability of the aptasensor is estimated for AβO detection in real cerebrospinal fluid and serum samples with acceptable signal recoveries, offering a viable, sensitive, and promising approach for the early diagnosis of AD.