Visual detection of miRNA using peroxidase-like catalytic activity of DNA-CuNCs and methylene blue as indicator

In this study, we developed a colorimetric method which is primarily based on the limited amount of redox in response to the miRNA target analyte binding for the determination of the miRNA, which is used as a biomarker to confirm the clinical diagnosis of cancers such as breast cancer. This method is on the basis of the peroxidase-like property of DNA templated copper nanoclusters (DNA-CuNCs). In this research, it was found that the DNA (poly T) stabilized green emitting CuNCs which exhibited enzyme-like peroxidase activity. After hybridization of miRNA with DNA-CuNCs probe and duplex formation, CuNCs catalyzed the oxidation of the methylene blue (MB) substrate, which can interact easily with DNA/miR-155 heteroduplex. Applying the optimal conditions, the absorbance of MB decreased by increasing the target miRNA-155 with in a dynamic range from 1.0 pM to 10.0 nM down to a detection limit (LOD) of 0.6 pM. The DNA-CuNCs/MB complex was designed to develop a facile, cheap, and fast colorimetric assay for detection of miRNA through MB oxidation by DNA stabilized CuNCs.