CRISPR/Cas trans-cleavage activity in pathogen detection: research progress and innovations.

The trans-cleavage activity of CRISPR/Cas systems has catalyzed significant progress in molecular diagnostics. Compared with traditional methods such as polymerase chain reaction (PCR) and its derivatives, CRISPR/Cas diagnostics are often credited with high specificity, portability, and visual readout. Among various CRISPR systems, CRISPR/Cas9, CRISPR/Cas12, and CRISPR/Cas13 have been extensively applied in pathogen detection owing to their distinct target-recognition and nucleic acid-cleavage mechanisms. In particular, Cas12- and Cas13-based systems exploit target-activated trans-cleavage activity for sensitive signal amplification, whereas Cas9-based diagnostic platforms generally rely on sequence-specific cis-cleavage. This review assesses the integrated CRISPR/Cas detection workflow from sample collection and processing through final result output, and systematically analyzes the intrinsic characteristics of Cas effector proteins with respect to target enrichment, reporter molecules, readout formats, sample background, and validation design. Based on a practical application-oriented framework, we analyzed the adaptability of various CRISPR/Cas systems in distinct scenarios, including point-of-care screening, quantitative laboratory testing, and multiplex pathogen identification. In addition, we highlight engineering innovations derived from mechanistic investigations of Cas9, Cas12, Cas13 and Class I CRISPR systems, discuss the specific diagnostic bottlenecks these effectors can resolve, and outline remaining challenges requiring further optimization prior to clinical translation.