Switchable electrochemical aptasensor for amyloid-β oligomers detection based on triple helix switch coupling with AuNPs@CuMOF labeled signaling displaced-probe.

The aggregation of amyloid-β oligomers (AβOs) with extremely strong neurotoxicity has been proved to be the main pathogenesis of Alzheimer's disease (AD). For sensitive quantification of AβOs, a switchable electrochemical aptasensor is proposed. Metal organic framework carrying Au nanoparticles (AuNPs@CuMOF) has been used to label signaling displaced-probe (SD), which formed triple helix switch (THS) by hybridizing with label-free anti-AβOs aptamer (Apt) on the electrodeposited palladium electrode (EPd). Thus, a relatively strong response of differential pulse voltammetry (DPV) was produced (switch on). With the specific binding between AβOs and Apt, the DPV response obviously decreased, owing to destroyed structure of THS and the separation of AuNPs@CuMOF/SD from the EPd (switch off). The mode of "switch on-off" can dramatically enhance the AβOs-dependent DPV intensity change. As a result, the switchable EA exhibited excellent selectivity and sensitivity with the linear range from 0.5 fM to 500 fM and the detection limit of 0.25 fM. When evaluating the AβOs of artificial cerebrospinal fluid (aCSF) samples, the switchable EA exhibited desirable feasibility, and the results are basically consistent with the enzyme linked immunosorbent assay (ELISA). The work could provide a potential tool of the AD diagnosis and a bright future in clinical applications.