DNAzyme-driven tripedal DNA walker triggered hybridization chain reaction for label-free electrochemical detection of Alzheimer’s tau protein

The tau protein is considered to be a reliable molecular biomarker of Alzheimer's disease (AD). Developing sensitive and reliable techniques for tau protein detection is a vital task. In this work, we designed a label-free electrochemical aptasensor for tau protein quantification based on Mg2+-DNAzyme (MNAzyme)-driven tripedal DNA walker. With the assistance of MNAzyme, free-running tripedal DNA walkers could rapidly and continually scissor DNA molecular beacon (MBs), and the fragment as a primer initiated the hybridization chain reaction (HCR) process generating a huge amount of long DNA strand containing many adenines. Following that, the strand with long-repeated adenines (HCR product) may absorb numerous AgNPs on the surface of electrode for electrochemical stripping analysis. Benefiting from MNAzyme-tripedal DNA walker and HCR triple signal amplification, we achieved a superior detection limit of 0.43 fM as well as a broad linear range of 1 fM to 0.1 nM. After being applied to tau protein detection in human serum samples, this novel electrochemical aptasensor demonstrated a high degree of anti-interference, and reproducibility, indicating its great potential for bioanalysis in complex biological environments.