miRNA-21 rapid diagnosis by one-pot synthesis of highly luminescent red emissive silver nanoclusters/DNA

microRNAs (miRNAs) are significant biomarkers either for probing cellular events or disease diagnosis. Compared to regular RNA, miRNAs possess short length and low abundance with sequence homology, which results in major challenges on the determination of these biomarkers. Thus, developing a simple, rapid, and effective technique for qualitative and quantitative analysis of miRNAs is urgent in clinical diagnosis, pathogenesis, and various medical therapies. Herein, DNA-silver nanoclusters (DNA/AgNCs) have been synthesized by a specific DNA scaffold containing a cytosine enriched fragment and a capitation agent with high selectivity probe, to design a Forster resonance energy transfer (FRET) sensing platform for miRNA-21 detection. A duplex miRNA-21/DNA probes structure is formed by introducing a red-emitting synthesized DNA/AgNCs, as a FRET donor, to miRNA-21 in the presence of a near-infrared (NIR)-emitting probe-modified Cy5.5, as a FRET acceptor. These sequences produced a duplex structure which could be utilized as a bridge for the successful transferring of the energy from DNA/AgNCs excited to Cy5.5 at steady state. This hybridized structure could result in the enhancement of Cy5.5 fluorescence intensity in a linearly proportional manner toward miRNA-21 concentration as a target. We believe this asdesigned FRET-based technique owning high selectivity, low detection limit (4.0 x 10(-3) nM), and a wide dynamic ranges of 0.02-100.0 nM, can be introduced as a new advanced method to develop specific miRNAs-based clinical diagnoses.