Non-SELEX isolation of DNA aptamers for the homogeneous-phase fluorescence anisotropy sensing of tau Proteins

Herein, we report for the first time the isolation of DNA aptamers directed against the whole tau protein, an important Alzheimer's disease (AD) biomarker. Non-SELEX approach based on the capillary electrophoresis partitioning technique was employed to isolate a high-affinity DNA sequence pool towards the target in only three rounds and one working day. High-throughput sequencing was next performed and the recognition ability of five selected aptamers was preliminary evaluated by surface plasmon resonance using the protein target immobilized on the chip. Finally, the analytical potential of the most affine aptamer was demonstrated through the design of a homogeneous-phase fluorescence anisotropy assay. This DNA aptamer was found to be able to recognize not only the whole τ-441 but also the τ-381, τ-352, τ-383 isoforms. The sensing platform allowed the determination of these four targets with a detection limit of 28 nM, 3.2 nM, 6.3 nM and 22 nM, respectively.