CdTe QD-CeO2 Complex as a Strong Photoelectrochemical Signal Indicator for the Ultrasensitive microRNA Assay.

The photoelectrochemical (PEC) signal can be enhanced by constructing sensitization structures containing photoactive materials and appropriate sensitizers. However, usually, the photoactive materials and sensitizers were separated in independent nanostructures, thereby producing long electron-transfer path and large energy loss, which could further result in limited photoelectric conversion efficiency and PEC signals. Herein, we designed a novel sensitization nanostructure simultaneously containing the photoactive material cerium dioxide (CeO2) and its sensitizer CdTe quantum dots (QDs) as the strong PEC signal indicator (CdTe QD-CeO2 complex), which prominently enhanced photoelectric conversion efficiency because of the shortened electron-transfer path and reduced energy loss. The proposed CdTe QD-CeO2 complex was used to construct a PEC biosensor for achieving ultrasensitive determination of microRNA-141 (miRNA-141) coupling with target converting amplification and DNA supersandwich structure amplification. The designed PEC biosensor demonstrated a wide linear range from 0.5 fM to 5 nM with a detection limit of 0.17 fM for miRNA-141. Impressively, this work provided a new and strong PEC signal indicator for the construction of  PEC sensing platform and would extend the application of PEC sensors in bioanalysis and early disease diagnosis.