Signal amplified colorimetric nucleic acid detection based on autocatalytic hairpin assembly

Herein, a nucleic acid assay based on autocatalytic hairpin assembly (ACHA) was proposed. In this system, two split G-quadruplex sequences were integrated into H1 and H2, respectively. And a DNA strand with the same sequence to target DNA was integrated into the assistant hairpin H3. In the presence of target DNA, the hairpin structure of H1 was opened and catalytic hairpin assembly (CHA) was activated, and then a series of DNA assembly steps based on the toehold-mediated DNA strand displacement were triggered and the product H1-H2 with sticky ends on both sides was formed. On the one side of H1-H2, the split two G-quadruplex sequences were close enough to form the intact G-quadruplex for the signal readout. At the same time, two sticky ends on the other side of H1-H2 hybridized with H3 and a new sticky end with the sequence same to the target DNA was exposed, which can immediately trigger the autocatalytic hairpin assembly reaction, and then the reaction rate of CHA was effectively accelerated and the colorimetric signal was significantly amplified. This ACHA signal amplified strategy has been successfully applied for the rapid and colorimetric nucleic acid detection.