A three-dimensional DNA walker and silver nanoparticles promoting lattice-strain-driven photo-induced electron transfer for high-performance semi-homogeneous biosensing

Abstract

As an important tumor marker, the ultra-sensitive detection of low-abundance microRNAs provides important data support for early warning of tumors. Herein, taking microRNA-141 as the target model, a novel enzyme-free semi-homogeneous photoelectrochemical (SHO-PEC) biosensor was designed by entropy-driven three-dimensional (3D) DNA walker with exponential signal amplification, magnetic enrichment and separation of pseudo-targets, bridged CdTe@ZnS quantum dots to promote photocathodic current enhancement, and in situ generated silver nanoparticles (NPs) to accelerate charge separation. In this protocol, ZnS shell passivates the surface defects of the soft core CdTe, introducing considerable strain that causes electrons to extend towards the shell, which is responsible for the higher photocurrent response. Also, the Ag NPs enable ultrafast photogenerated electron transfer by forming Schottky junctions. These two unique sensitized mechanisms were proposed for the first time in PEC sensing. Moreover, a one-step simple electrode modification strategy avoids tedious layer-by-layer assembly and rinsing steps. These make the "signal-on" SHO-PEC biosensor with remarkable advantages of high sensitivity, good specificity, strong reliability, fast speed, easy operation, and low cost. This research provides a new initiative for the development of PEC sensing platforms with excellent comprehensive performance.