Fluorescent aptasensor based on conformational switch-induced hybridization for facile detection of β-amyloid oligomers.

Aβ oligomers (AβO) are a dominant biomarker for early Alzheimer's disease diagnosis. A fluorescent aptasensor coupled with conformational switch-induced hybridization was established to detect AβO. The fluorescent aptasensor is based on the interaction of fluorophore-labeled AβO-specific aptamer (FAM-Apt) against its partly complementary DNA sequence on the surface of magnetic beads (cDNA-MBs). Once the FAM-Apt binds to AβO, the conformational switch of FAM-Apt increases the tendency to be captured by cDNA-MBs. This causes a descending fluorescence of supernatant, which can be utilized to determine the levels of AβO. Thus, the base-pair matching above 12 between FAM-Apt and cDNA-MBs with increasing hybridizing free energies reached the ascending fluorescent signal equilibrium. The optimized aptasensor showed linearity from 1.7 ng mL to 85.1 (R = 0.9977) with good recoveries (79.27-109.17%) in plasma. Furthermore, the established aptasensor possesses rational selectivity in the presence of monomeric Aβ, fibrotic Aβ, and interferences. Therefore, the developed aptasensor is capable of quantifying AβO in human plasma and possesses the potential to apply in clinical cases.