An aptamer-mediated EXPAR fluorescence biosensor for early and sensitive detection of Aβ42 and Aβ40

Alzheimer's disease (AD) is a common neurodegenerative disorder with increasing cases worldwide. Early screening is important for AD prevention and treatment, but current methods still face many challenges.

To address these challenges, we developed a simple and novel molecular beacon (MB) fluorescent biosensor. This sensor combines aptamers with exponential amplification reaction (EXPAR). Through special design of the EXPAR templates, the sensor achieves triple signal amplification. It showed a limit of detection (LOD) of 110 fM for Aβ42 and 300 fM for Aβ40, exhibits high sensitivity. The coefficient of variation (CV) for detecting different target concentrations ranged from 4.42% to 8.85%, showing good repeatability. We also applied this sensor to detect these biomarkers in plasma samples from AD patients. The spike recovery rates were 104.67%-109.3% for Aβ42 and 104.2%-106.93% for Aβ40, demonstrating strong resistance to plasma matrix interference. Due to the specificity of aptamers and nucleic acid design, this method allows simultaneous detection of multiple targets (e.g., Aβ42, Aβ40) in the same system, improving detection efficiency and reliability in complex samples.

Compared with traditional Aβ detection methods such as ELISA and colorimetry, our method shows 10-10⁴ times higher sensitivity. Compared with emerging techniques like electrochemical detection and single-molecule array, our sensor has the advantages of stronger resistance to plasma matrix interference, more stable results, lower cost and biotoxicity, simpler operation and better biocompatibility and potential of multiple-target detection. These features make it a promising tool for high-throughput early screening of AD, with potential to advance early diagnosis.