An Electrochemiluminescence Aptasensor Based on Luminescent-Nanospheres Coupling With Reconfigurable Switchable System for Detection of Oligomeric Aβ

Excessive oligomeric Amyloid- β (A β Os) in the brain induces strong neurotoxicity and are a major causative marker of Alzheimer's disease (AD). Herein, an exemplary electrochemiluminescence (ECL) aptasensor for A β Os that coupled a triple-helix switchable system (THSS) with gold-doped Ru(bpy) 3 2+ /copper luminescent-nanospheres (RuCu@AuLNs) was successfully developed. In brief, the anti-A β Os aptamer (Apt) with two symmetric arms and RuCu@AuLN-marked signal transduction DNA (RuCu@AuLNs-ST) perfectly constructed the THSS on a gold electrode surface via hybridization reaction. At this point, the THSS was closed, and a strong initial ECL signal ( I ECL0 ) output was generated. Once A β Os appeared, they specifically bound with Apt and opened the THSS, releasing RuCu@AuLNs-ST from electrode surface, and degressive ECL signal ( I ECL1 ) was obtained. Thus, the aptasensor detected A β Os-dependent I ECL1 change (Δ I ECL1 = I ECL0 − I ECL1 ) with a concentration range of 1 fM to 1 pM with a low detection limit of 0.5 fM, and demonstrated good reliability and practicality in human serum. Additionally, the reconfigurability of the sensor allows it to be continuously reused up to 5 times at a concentration of 1 fM A β Os. The developed ECL aptasensor could be used as a cost-effective tool for early diagnosis of AD. Moreover, the strategy has promising application in the bioassays of various analytes.