Advancing Alzheimer’s biomarker Detection: A hairpin Aptamer-Based competitive electrochemical biosensor for trace Amyloid beta 40 analysis
Accurate detection of Alzheimer’s disease (AD) core biomarkers in body fluid is critical for identifying latent asymptomatic AD patients and prediction AD progress. Amyloid beta 1–40 (Aβ-40) as one of the core biomarkers, is expected to be an early diagnostic indicator for AD. Here, we establish a competitive method based on hairpin-structured aptamer for rapid and highly sensitive detection of Aβ-40 using square wave voltammetry (SWV). A hairpin aptamer with redox-active moiety methylene blue (MB) are immobilized on a gold working electrode as a recognition element. In the detection, a short complementary oligonucleotide strand is first introduced to switch on the hairpin, whereafter the targets Aβ-40 join in and selectively react with the aptamer in a competitive manner with the complementary strand, leading to the changes in the proximity of MB to the electrode and thereby in the electrochemical signal. Various parameters such as aptamer concentration, complementary chain length, incubation time, and temperature were optimized to achieve maximum sensing performance. By introducing a complementary chain, the sensor significantly reduces the detection limit to 7.14 pg/mL, with a dynamic range of 20 pg/mL to 200 ng/mL. Additionally, high selectivity of the sensor for Aβ-40 monomer (Aβ-40 m) over other forms of Aβ peptides has been validated. The hairpin-mediated detection method enables rapid, facile and highly sensitive detection of Aβ-40 using low-cost screen-printed electrode (SPE) platform, providing a wide range of possibilities for the early diagnosis of AD in point-of-care technologies (POCT).
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