Framework-Hotspot Enhanced Trans Cleavage of CRISPR-Cas12a for Clinical Samples Detection.

The trans-cleavage property of CRISPR-Cas12a system makes it an excellent tool for disease diagnosis. Nevertheless, most methods based on CRISPR-Cas system still require pre-amplification of the target to achieve the desired detection sensitivity. Here we generate Framework-Hotspot reporters (FHRs) with different local densities to investigate their effect on trans-cleavage activity of Cas12a. We find that the cleavage efficiency increases and the cleavage rate accelerates with increasing reporter density. We further construct a modular sensing platform with CRISPR-Cas12a-based target recognition and FHR-based signal transduction. Encouragingly, this modular platform enables sensitive (100 fM) and rapid (<15 min) detection of pathogen nucleic acids without pre-amplification, as well as detection of tumor protein markers in clinical samples. The design provides a facile strategy for enhanced trans cleavage of Cas12a, which accelerates and broadens its applications in biosensing.

CRISPR/Cas systems for the detection of nucleic acid and non-nucleic acid targets.

Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas) systems are becoming powerful tools for disease biomarkers detection. Due to the specific recognition, cis-cleavage and nonspecific trans-cleavage capabilities, CRISPR/Cas systems have implemented the detection of nucleic acid targets (DNA and RNA) as well as non-nucleic acid targets (e.g., proteins, exosomes, cells, and small molecules). In this review, we first summarize the principles and characteristics of various CRISPR/Cas systems, including CRISPR/Cas9, Cas12, Cas13 and Cas14 systems. Then, various types of applications of CRISPR/Cas systems used in detecting nucleic and non-nucleic acid targets are introduced emphatically. Finally, the prospects and challenges of their applications in biosensing are discussed.