Signal‐On Photoelectrochemical Aptasensor Amplified by Exciton Energy Transfer and Exonuclease‐Aided Target Recycling

Abstract

AbstractAn enhanced photoelectrochemical (PEC) aptasensor was developed by coupling exciton energy transfer (EET) with exonuclease aided target recycling. Thrombin was selected as the target analyte. CdS quantum dots (QDs) as energy donors were first modified on the TiO2 film to form a TiO2/CdS heterostructure, and then complementary DNA (cDNA) of the thrombin aptamer probe (pDNA) was immobilized. Au nanoparticles (AuNPs) as energy acceptors were labeled at the 3′ end of pDNA to form AuNP‐pDNA composites. After pDNA hybridized with cDNA, the EET occurred and the photocurrent reduced evidently. When the mixture of thrombin and RecJ exonuclease was introduced, pDNA specifically bound with thrombin, leading to the separation of AuNP‐pDNA composites from the electrode. As RecJ exonuclease could cleave single‐strand pDNA from 5′–3′, the captured thrombin was set free and it recurrently binds with the rest of pDNA. As a result, the EET was broken, to a large extent, and the photocurrent clearly picked up. This signal‐on PEC aptasensor shows a low detection limit and good selectivity for target analysis.