Concatenated DNA Circuit-Assembled DNAzyme as an Amplified Quencher for MicroRNA Detection

In this study, we designed a fluorimetric assay for ultrasensitive determination of microRNA-141 based on WS2 quantum dots (WS2 QDs) and concatenated DNA circuit-assembled DNAzymes. WS2 QDs are synthesized using sodium tungstate and cysteine as W and S sources, and the use of biomass materials as a precursor is environment-friendly. The presence of microRNA-141 can trigger the CHA and HCR, leading to the formation of long dsDNA nanochains with numerous HRP-mimicking DNAzymes. The o-phenylenediamine structure was oxidized to 2,3-diaminophenazine by the DNAzymes. WS2 QDs could be quenched by 2,3-diaminophenazine via the inner filter effect. This method is highly sensitive for the analysis of microRNA-141 with a limit of detection of 2.7 fM. The designed strategy has no measurable response to four other microRNAs. The WS2 QDs-based sensor was used for the microRNA-141 assay in human serum and microRNA-141 expression in MDA-MB-231 cells. This newly developed biosensor shows great potential for the analysis of biomarkers and early diagnosis of microRNA-related diseases.