Ternary hybrids accelerated photoelectrochemical biosensor for sensitive detection of Alzheimer's disease biomarker

Amyloid β oligomer (AβO) is not only a crucial biomarker but also a potential therapeutic target for Alzheimer's disease (AD). Here, a type of ternary photoactive hybrids (CdS/ZnS/Bi₂Se₃) was used as a substrate material to construct a photoelectrochemical (PEC) biosensor for dual-quenching detection of AβO. Due to the cooperative band gap excitations and multi-interfacial charge transfer of the three components, CdS/ZnS/Bi₂Se₃ ternary hybrids possessed self-enhanced photocurrent, which significantly boosted PEC responses. The broad-spectrum absorption and peroxidase-mimicking catalytic property of PtCu nanoflowers (NFs) achieved the synergistic dual-quenching effect, which displayed a more sensitive response than common single-quenching PEC biosensors. Impressively, an efficient dynamic signal amplification strategy was established by DNA cascade reaction-activated DNA walker, improving the walk speed and high reaction efficiency. As a result, the constructed biosensor realized the detection of AβO ranging from 20 fM to 10 nM with a detection limit of 4.4 fM. In comparison to previously reported methods, the biosensor enabled the reliable detection of AβO in blood specimens from AD patients and healthy volunteers, demonstrating high sensitivity, specificity, stability, and reproducibility. By simply replacing the aptamer sequences, this strategy could be applied for other biomarker detection with a high potential to inspire innovative sensing approaches, offering some useful help for biomedical research and disease diagnosis.