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

Abstract

An 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.

Energy Transfer between Semiconducting Polymer Dots and Gold Nanoparticles in a Photoelectrochemical System: A Case Application for Cathodic Bioanalysis

“…We report herein the energy transfer (ET) between semiconducting polymer dots (Pdots) and gold nanoparticles (Au NPs) in a photoelectrochemical (PEC) system and its feasibility for cathodic PEC bioanalysis application. − Different from anodic bioanalysis, the intrinsic electron reduction reaction occurs at the photocathode/electrolyte interface, which makes the absorbed reductive molecules have no influence on the reduction reaction, resulting in good anti-interference to reductive agents in the samples . Previously, we have observed the unique interparticle interplay between the photoactivated quantum dots (QDs) and noble metal (Au or Ag) NPs in the PEC nanosystem. , The optical spectral overlap makes possible the simultaneous activation of these particles, and the stimulated surface plasmon resonance (SPR) and local electric fields thereby could regulate the excitonic responses in the QDs. ,, This phenomenon promptly ignited increasing interest among the community and the research on ET-based PEC bioanalysis has since been actively pursued. − For example, enhanced resonance ET between reduced grapheme oxide (RGO)-Au NPs and CdTe QDs enables its use for different target molecules, and the strong exciton energy transfer (EET) effect of Au NPs and CdSe QDs was applied in the highly sensitive detection of DNA methyltransferase (MTase) . Recently, our group also utilized the TATA-binding protein to bend the Au NPs capped DNA sequence to affect the interparticle distance and then triggered the transition of the interplay from the CdS QDs-Au NPs to the CdS QDs-Ag NPs systems by a catalytic Ag deposition process .…”