Engineering of multifunctional carbon nanodots-decorated plasmonic Au@Ag nanoenzymes for photoelectrochemical biosensing of microRNA-155

Abstract

Herein, the multifunctional carbon nanodots (CDs)-decorated plasmonic Au@Ag nanoenzymes coupled with Ti2C/Ag2S composites were proposed for photoelectrochemical (PEC) biosensing of microRNA. Two-dimensional (2D) Ti2C MXenes-sensitized Ag2S quantum dots (QDs) (Ti2C/Ag2S composites) acquired an initial photocurrent. After immobilization of a hairpin subsidiary probe (S1) onto the Ti2C/Ag2S composites photoelectrode surface, the target microRNA-associated bipedal DNA walker performed the opening of S1 for forming triple helix molecules. Then the CDs-decorated Au@Ag core–shell (Au@Ag@CDs) nanocuboids were introduced into the PEC biosensing platform through target-induced triple helix molecules. The Au@Ag@CDs nanocuboids as a multifunctional signal amplifier not only competitively captured the irradiating light and electron donors to weaken the PEC signal, but also quenched the photocurrent response resulting from energy transfer between plasmonic bimetallic Au@Ag nanocuboids and Ag2S QDs. Additionally, the Au@Ag and CDs in Au@Ag@CDs nanocuboids displayed a synergistic catalytic effect, and could serve as peroxidase nanoenzymes to catalyze the production of precipitates onto the biosensor surface, resulting in a significantly decreased photocurrent. Based on the plasmonic Au@Ag@CDs nanoenzymes coupled with Ti2C/Ag2S composites, microRNA-155 was ultrasensitively detected with a wide linear range (1–10,000 fM) and a low limit of detection (0.83 fM). Moreover, the engineered plasmonic Au@Ag@CDs nanoenzymes offer an environmentally friendly and multifunctional signal amplifier for fabricating PEC biosensor and have potential applications in biomarkers detection and disease diagnostics.