Amplified fluorescence biosensing system for microRNA detection based on a novel DNA-network nanoarchitecture

A unique DNA reticular nanostructure was successfully assembled using two kinds of hairpin DNA probes (HAPs) via a target-induced circular amplification strategy for the fluorescence biosensing of microRNA-21 (miRNA-21). First, a cyclic DNA-1/DNA-2 template was prepared. Then, the target miRNA-21 was hybridized with the singlestranded DNA template, triggering cyclic polymerization, shearing, and replacement amplification reactions via polymerase and endonuclease activity, which resulted in great accumulation of the DNA-2 product. Then, DNA-2 was used to open the hairpin structure HAP1, which initiated the polymerase-aided HAP hybridization-extension process. Thus, DNA reticular nanostructures with abundant double-stranded DNA (dsDNA) were assembled. By intercalating a large amount of SYBR Green I fluorescent dye into the plentiful dsDNA of the nanostructures, a significantly amplified fluorescent signal was obtained, allowing the sensitive detection of miRNA-21. The newly developed DNA nanostructures will be widely used in biosensors and functional nanomaterials with great prospects. Herein, this amplified fluorescence biosensing platform was applied for an miRNA-21 assay in human cancer cells with good accuracy, showing promising applications in biological analysis and clinical testing.