Assembling G-wire-induced pyrene excimer switching for microRNA amplified detection based on exonuclease III-assisted target recycling and Fe3O4@PDA nanoparticles

We reported a novel assembled G-wire-induced pyrene excimer switching probe for microRNA (miRNA) amplified detection on the basis of exonuclease III (Exo III)-assisted target recycling and Fe3O4@PDA nano-particles. The multifunctional hairpin (HP) probe recognized and effectively bound to target miRNA, which formed a 3 '-blunt terminal for Exo-III digestion and miRNA regeneration to initiate another Exo III-mediated cycling cleavage. After digestion, numerous HP-caged c-myc sequences were released, which were positively related to target miRNA and folded to the parallel G-quadruplex with K+. Additionally, Fe3O4 polydopamine nanoparticles (Fe3O4@PDA NPs)-based magnet separation was conducted to reduce background fluorescence signal, and parallel G-quadruplexes self-asembled into filamentous G-wires with Mg2+. G-wires generated from 5 '-terminal pyrene-labeled c-myc sequences made close distance between two labeled pyrene molecules, and induced the "turn-on" fluorescence signal of pyrene excimer switching. Moreover, gamma-cyclodextrin (gamma-CD) was added, which promoted pyrene moiety, causing signal amplification in pyrene excimer fluorescence. Therefore, miRNA was efficiently measured within the homogeneous solution. This method detected miRNA within the dynamic range of 1 pM to 5 nM, with the miR-141 limit of detection (LOD) being 99 fM. It distin-guished perfect-matched and mismatched target miRNAs, and showed an accurate detection of miRNA levels in different cell lines and favorable reproducibility when analyzing miRNAs within spiked serum samples. We propose a promising method for G-wire-based biosensing in disease-related biomarkers detection.