A dual-mechanism-driven electrochemiluminescence aptasensor for sensitive detection of β-amyloid peptides

Abstract

β-Amyloid (Aβ) peptides can bind both Cu²⁺ and heme cofactors simultaneously to form heme–Cu²⁺–Aβ complexes, which are proposed to generate toxic partially reduced oxygen species (PROS, e.g., H₂O₂) and play a vital role in Alzheimer's disease (AD). In this paper, a competitive dual-mechanism-driven electrochemiluminescence (ECL) aptasensor integrating the synergistic enhancement and steric hindrance effect was described for Aβ detection. Specifically, graphite carbon nitride (g-C₃N₄) as an effective ECL luminescent substrate and Au nanoparticles were sequentially assembled on the Au electrode surface, and then a thiol-modified aptamer for capturing Aβ peptide was attached to the surface of the electrode through the Au–S bond. Aβ peptides were simultaneously incubated with heme and Cu²⁺, and the forming heme–Cu²⁺–Aβ complexes were subsequently anchored on the electrode through the specific recognition between the target Aβ and the aptamer. When the concentration of the target Aβ is low, the synergistic enhancement effect arising from K₂S₂O₈ with in situ generated H₂O₂ is predominant, resulting in an increase in the ECL signal of g-C₃N₄. In contrast, when the concentration of Aβ is high, the steric hindrance effect generated from heme–Cu²⁺–Aβ complexes is dominant, leading to a decrease in the ECL signal. The present sensor exhibits a favorable linear response for the detection of Aβ with a relatively low detection limit of 0.24 pM, and provides a more sensitive and selective platform for bioanalysis.