Label-free fluorescent detection of microRNA-155 based on synthesis of hairpin DNA-templated copper nanoclusters by etching (top-down approach)

In this study, we have reported a new approach for sequence specific microRNA-155 (miRNA-155) detection by water soluble luminescent copper nanoclusters. The method is based on the shifts in the fluorescence emissions of oligonucleotide-templated copper nanoclusters (DNA-CuNCs) and can be regarded as the first instance of using fluorescent CuNCs for the detection of microRNA by forming DNA-RNA heteroduplex. The as-prepared CuNCs exhibited a strong fluorescence enhancement at 510 nm and a red shift (60 nm) when bonded to the target miRNA-155 (DNA-RNA heteroduplex formation). Under the optimal conditions, the fluorescent intensity of DNA-CuNCs increased by the increasing the target miRNA-155 with in a dynamic range from 5.0 × 10−12 to 1.0 × 10−8 M down to a detection limit (LOD) of 2.2 × 10−12 M. The target miRNA is selectively discriminated from mismatched miRNA by this method. The method was further applied to the determination of miRNA spiked human serum samples. Overall, the nanobiosensor showed the potential of becoming a potential alternative tool for the detection of miRNA-155 in biomedical research and early clinical diagnostic studies.