High-fidelity detection of DNA combining the CRISPR/Cas9 system and hairpin probe.

Methods that enable specific and sensitive detection of DNA are greatly required for high-fidelity sequence measurement and single-nucleotide variations (SNVs) genotyping. The CRISPR (clustered regularly interspaced short palindromic repeats)/Cas systems have provided revolutionary tools for detecting nucleic acids. However, most of the current CRISPR/Cas-based DNA biosensing platforms suffer from inherent off-target effects of Cas proteins and require pre-amplification processes, which compromise the analytical fidelity. In this work, a CRISPR/Cas9-triggered hairpin probe-mediated biosensing method (namely CHP) was used to directly read the original DNA sequences, while effectively neutralizing the off-target effect and achieving high sensitivity. This technique can quantify DNA targets with a limit of detection (LOD) at the attomole level and identify SNVs with allelic fractions as low as 0.01%~0.1%. Moreover, we show that the CHP system is applicable in detecting mutations in serum samples without DNA isolation steps. Collectively, the CHP system is a sensitive and high-fidelity platform, which promises a great potential for providing robust tool for DNA sequence analysis and SNVs genotyping.