A signal-locked clamped hybridization chain reaction nanoamplifier for rapid and highly sensitive analysis of Aβ42.

Amyloid-beta 42 (Aβ42) is a core biomarker associated with Alzheimer's disease (AD), but accurate quantification of low-abundance plasma Aβ42 remains challenging because of matrix interference, limited assay sensitivity, and time-consuming procedures in conventional methods. Herein, we developed an enzyme-free fluorescence biosensing platform integrating a triple-helix aptamer probe (THAP) with clamped hybridization chain reaction (cHCR), termed T-cHCR, for sensitive Aβ42 analysis. In this system, Aβ42 recognition induces controlled release of a trigger probe from the triplex-locked THAP module, which subsequently initiates a two-hairpin cHCR cascade for low-background signal amplification. Under optimized conditions, the T-cHCR assay exhibited a linear response to Aβ42 from 1 to 1000 pg/mL with a limit of detection of 1.16 pg/mL, showing an 8.1-fold lower LOD than the manufacturer-reported minimum detectable dose of the ELISA kit used in this study. The assay also displayed acceptable specificity, reproducibility, and storage stability. Preliminary analysis of clinical plasma samples showed significantly different Aβ42 levels between AD patients and age-matched healthy controls, supporting the potential of T-cHCR for further validation in plasma AD biomarker analysis. Overall, this integrated THAP-cHCR strategy provides a rapid, enzyme-free, and low-background approach for ultrasensitive plasma Aβ42 detection.