Simple and label-free colorimetric detection of microRNA using hairpin DNA probe and gold nanoparticles

Abstract

In this study, we developed a label-free colorimetric miRNA detection method based on hairpin DNA probe and gold nanoparticles. The proposed method involves a unique DNA probe complex composed of hairpin DNA strand and trigger strand. In the presence of target miRNA, the closed hairpin structure changes into linear form due to complementarity of target to the loop region of the hairpin strand. This allows primer extension reaction by Klenow Fragment (exo-) to occur, leading to a robust reaction that displaces both of the bound target miRNA and trigger strand. The miRNA can then be recycled to open new hairpin probes for signal amplification. The displaced trigger strands induce gold nanoparticle aggregation, which serves as the signaling mechanism for this method. The whole assay can be achieved in 95 minutes and allows quantitative detection of miR-141 in the dynamic range of 500fM to 100nM. The proposed strategy proved to be highly sensitive, selective, rapid, and cost-effective, showing potential as a tool for use in clinical diagnosis and miRNA analysis.