Ultrasensitive PEC aptasensor based on one dimensional hierarchical SnS2| oxygen vacancy-WO3 co-sensitized by formation of a cascade structure for signal amplification

Herein, we developed a photoelectrochemical (PEC) aptasensing platform that relies on a dual-signal amplifi-cation strategy. The proposed PEC system consists of a one dimensional (1D) hierarchical SnS2 vertical bar OV (oxygen vacancy)-WO3 nanorods (NRs) sensitized by CdS quantum dots (QDs)/TCPP (TCPP: meso-tetra(4-carbox-yphenyl)-porphine), and exonuclease III-assisted target recycling. As a photoactive heterojunction, SnS2 vertical bar OV-WO3 nanocomposite exhibits a PEC signal similar to 11 times higher than pure WO3 NRs due to the enhanced separation efficiency of photo-generated carriers. Moreover, it was also used to immobilize a hairpin DNA3 probe labeled with CdS QDs/TCPP, which formed a co-sensitization cascade structure with SnS2 vertical bar OV-WO3 NRs on the sensor surface due to the well-matched energy levels. This special cascade structure effectively shortened the electron-transfer path and inhibited charge recombination, thereby improving the PEC performance. The addition of the target vascular endothelial growth factor 165 (VEGF(165)) triggered the exonuclease III-assisted target recycling to generate plentiful DNA sequences (S1). S1 was specifically hybridized with HP3 to unfold its hairpin structure. As a result, CdS QDs/TCPP detached from the sensor surface and SnS2 vertical bar OV-WO3 NRs, which destructed the co-sensitization cascade structure and minimized the PEC signals. The proposed PEC aptasensor exhibited a dy-namic determination range of 0.5 fM-10 nM, and a detection limit of 0.34 fM for VEGF(165).

Automated summary

A photoelectrochemical aptasensing platform with a dual-signal amplification strategy and exonuclease III-assisted target recycling was developed, showing improved performance and a detection limit of 0.34 fM for VEGF(165).