In-situ nucleic acid amplification induced by DNA self-assembly for rapid and ultrasensitive detection of miRNA

Background

To improve the sensitivity and specificity of nucleic acid detection, coupling two or more signal amplification systems is a feasible pattern, such as nucleic acid isothermal amplification coupling genome-editing technology, and cascaded DNA self-assembly circuits. And representative signal amplification strategies include loop-mediated isothermal amplification (LAMP), clustered regularly interspaced short palindromic repeats/associated proteins (CRISPR/Cas) systems, and catalyzed hairpin assembly (CHA). However, these detection strategies often require the enrichment of intermediate products, the replacement of reaction conditions and the design of multiple probes, which may seriously affect the reliability of detection results.

Results

Herein, we propose a novel nucleic acid detection system which is named as catalyzed hairpin assembly (CHA) coupled with embedded primer triggered isothermal amplification (CEA for short). DNA self-assembly probes in CEA contain a specially designed primer. When target nucleic acid (e.g., miRNA) initiates CHA reaction (the first signal amplification), the self-assembly product of CHA will expose a primer (named as embedded primer). The embedded primer will trigger a special nucleic acid isothermal amplification in situ, then generate plenty of double-stranded DNA products in 30 min with varying lengths (the second signal amplification). Compared to that of a typical CHA reaction, the sensitivity of CEA has increased by three orders of magnitude and the detection limit is as low as 0.228 fM. Besides, it has excellent detection performance in cancer and stem cell samples.

Significance

By coupling embedded primer with DNA self-assembly system, a new nucleic acid detection system (CEA) with one-step operation and dual signal amplification has been successfully established. Compared with traditional dual signal amplification systems, CEA can not only significantly improve the reaction efficiency, but also greatly reduce the difficulty of detection system design and experimental operation.