Nicking endonuclease-mediated primer exchange reaction for rapid and sensitive miRNA detection

Primer exchange reaction (PER) is a novel and simple nucleic acid-templated extension technique that has recently attracted much attention in the field of biosensing. However, current PER reactions have shown relatively slow rates and low amplification performances, resulting in long assay times and limited detection sensitivities. Here we report a nicking endonuclease-mediated PER reaction (named NEPER) that rapidly releases amplified DNA products by adding a nicking endonuclease to hydrolyze the hybridized double-stranded DNA (dsDNA), and consequently has a maximum speed that is thirty orders of magnitude greater than the maximum for conventional PER. We further combined a CRISPR/Cas12a signal readout technique and developed a cascade NEPER-CRISPR/Cas12a method that can detect miRNA-155 with a limit of detection (LOD) down to 3.1 fM. We also show that the NEPER-CRISPR/Cas12a can be used to detect targets in serum samples.