Enzyme-free colorimetric detection of MicroRNA-21 using metal chelator as label for signal generation and amplification

MicroRNAs (miRNAs) were reported to be potential tumor markers for early diagnosis of cancer. Due to its short sequence, low expression level and high susceptibility to degradation, the stable and sensitive detection method of miRNAs is arduous to establish. In this work, we designed a metal chelator (ethylenediamine tetraacetic acid disodium salt, EDTA•2Na) labeled oligonucleotides as the plasmonic signal supraregulator probe to control the generation of gold nanoparticles (AuNPs). Based on another complementary oligonucleotides of target miRNA labeling SiO₂ microparticles (SiO₂MPs) as the detecting platform, EDTA•2Na labeled oligonucleotide probes were immobilized on the SiO₂ platform through the sandwich structure in the presence of target miRNA. The sandwich chelating device could further chelate Au³⁺ to regulate the generation of AuNPs, resulting in colorimetric signal to qualitatively and quantitatively detect the concentration of microRNA-21 (miR-21). The results indicate that the proposed metal chelator -labeled signal amplification method has outstanding sensitivity (LOD = 8.9 fM) and excellent stability, which will be benefit for the early accurate diagnosis of miRNAs.