Label-free and self-assembled fluorescent DNA nanopompom for determination of miRNA-21

A label-free fluorescence method based on self-assembled DNA nanopompom has been developed for miRNA-21 detection. In the presence of miRNA-21, three DNA hairpin probes with split G-quadruplex assemble the DNA nanopompom. Based on the isothermal toehold-mediated DNA strand displacement reaction, the target miRNA can be catalytically recycled and trigger three DNA hairpin probes to self-assemble the DNA nanopompom and release the G-quadruplex. The formation of the G-quadruplex increases the fluorescence emission intensity of thioflavin. For thioflavin-based miRNA-21 detection, the excitation and emission wavelengths are set to 425 nm and 490 nm, respectively. The limit of detection for miRNA-21 is 0.8 pM according to F/F0 = 0.0031 × CmiRNA-21 + 1.0382 (R2 = 0.9978). This sensing system provides a low-cost, effective, and convenient method for miRNA detection, which holds great potential in biochemical diagnosis and clinical practice.