Rapid and simple separation and detection of Aβ42 in blood neuronal-derived extracellular vesicles using nanozyme-catalyzed colorimetric sensor.

The rapid separation and detection of neuronal-derived small extracellular vesicles (EVs) in plasma is essential for diagnosing and monitoring the progression of Alzheimer's disease (AD). In this study, we present a magnetic separation-assisted visual analysis strategy for detecting Aβ42-positive EVs (Aβ42+ EVs) using a nanozyme-catalyzed colorimetric sensor. EVs are first captured from plasma using Fe3O4@SiO2 core-shell nanoparticles functionalized with CD63 aptamers (Fe3O4@SiO2-AptCD63). Au@Pt nanozymes, modified with Aβ42 aptamers (Au@Pt-AptAβ42), then bind to the Aβ42 protein on the EVs, forming a sandwich structure (Fe3O4@SiO2-EVs-Au@Pt NPs). This structure catalyzes the oxidation of the substrate 3,3',5,5'-Tetramethylbenzidine (TMB), generating visual signals. The sensor demonstrates high sensitivity, with a detection range of 1 × 105 to 1 × 109 particles/mL and a low detection limit of 7.2 × 104 particles/mL. It was successfully used to detect Aβ42+ EVs in plasma samples from AD patients, showing significant promise for early AD diagnostics in clinical settings.