An Electrochemiluminescence Aptasensor Based on Luminescent‐Nanospheres Coupling With Reconfigurable Switchable System for Detection of Oligomeric A β

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.