Catalytic hairpin assembly coupled with Ir (III) complex sensitization strategy for split-type photoelectrochemical biosensing

Abstract

High-performance photoelectrochemical (PEC) assay of low-abundance microRNAs (miRNAs) still suffers from a challenge. Herein, a skillful magnetic extraction-assisted PEC biosensor has been developed based on miRNA-20b induced catalytic hairpin assembly (CHA) quenching the enhanced photoelectric signal of CdSe QDs and [Ir(ppy)2(phen-NH2)]+PF6−. A small amount of miRNA-20b can initiate the CHA amplification, and the separated Fe3O4 @SiO2-H1-H2 composites incorporation with CdSe QDs-S1 and the iridium (III) complex cause a decrease in the number of organic-inorganic hybrid nanomaterials in the liquid phase, thereby bringing about a proportional decrease in photoelectric signal. This flexible design and one-step electrode assembly contribute to the PEC biosensor with advantages of stability, reproducibility, as well as short-time consumption. Moreover, CHA amplification technique and organic-inorganic hybrid nanomaterial sensitization strategy make the detection more sensitive. In addition, the specific Watson-Crick base-pairing rules coupled with bio-functionalized superparamagnetic Fe3O4@SiO2 particles enable the PEC biosensor with excellent selectivity in serum samples. Particularly, instead of the iridium (III) complex as an intercalator in duplex DNAs for photocurrent readout, this split-type strategy endows a robust PEC biosensor and provides an alternative perspective for general detection of miRNAs.