Abstract
The emergence of clustered regularly interspaced short palindromic repeat (CRISPR) and CRISPR-associated proteins (Cas) system represents a revolutionary paradigm shift in molecular diagnostics, offering transformative potential for RNA analysis within the rigorous demands of forensic science. Conventional forensic RNA detection methodologies, such as reverse transcription-quantitative polymerase chain reaction (RT-qPCR) or microarray analysis, are significantly hampered by inherent limitations including complex, multi-step protocols requiring sophisticated laboratory infrastructure, pronounced susceptibility to inhibitors prevalent in complex forensic matrices (e.g., humic acids, heme, indigo dyes), and often inadequate sensitivity for trace or degraded samples typical of crime scenes, thereby failing to meet the critical operational imperatives of forensic practice: rapidity, high specificity, sensitivity, portability, and robustness against interference. This review posits that CRISPR-Cas-based RNA detection technology provides a groundbreaking solution by leveraging the programmable, sequence-specific recognition conferred by the synergistic interaction between a designed guide RNA (gRNA) and Cas effector proteins (e.g., Cas12a, Cas13a, Cas14). Upon target RNA binding, specific Cas enzymes undergo conformational activation, exhibiting collateral cleavage activity―a unique catalytic amplification mechanism where the enzyme non-specifically cleaves surrounding reporter molecules, enabling ultra-high sensitivity. To further enhance detection limits, CRISPR-Cas systems are strategically integrated with isothermal pre-amplification techniques like recombinase polymerase amplification (RPA) or loop-mediated isothermal amplification (LAMP), which efficiently amplify target RNA at constant temperatures, eliminating the need for thermal cyclers. This powerful cascade―isothermal pre-amplification followed by CRISPR-mediated sequence-specific recognition and collateral signal amplification―achieves exceptional sensitivity, often down to the single-molecule (attomolar) level, while drastically reducing analysis time to potentially 30-60 min. Crucially, the compatibility of CRISPR-Cas detection with simple, equipment-free readout systems, such as lateral flow strips (LFS) for visual colorimetric results or portable fluorescence/electrochemical sensors, facilitates true point-of-need (PON) forensic analysis directly at crime scenes, morgues, or field labs. This enables rapid applications like specific body fluid identification (e.g., distinguishing menstrual blood via miRNA, identifying saliva via mRNA), post-mortem interval (PMI) estimation through RNA degradation/expression patterns, donor age inference via age-related RNA markers, tissue identification, and microbial forensics, thereby accelerating investigative leads, minimizing sample degradation risks, and optimizing resource allocation. However, significant challenges impede widespread adoption, including persistent environmental interference inhibiting enzymes, fluctuations in Cas/amplification enzyme activity affecting reproducibility, a critical lack of standardized protocols and validated quality assurance/quality control (QA/QC) frameworks essential for forensic reliability and court admissibility, and current limitations in multiplex detection capability. Consequently, future research must prioritize overcoming multiplexing bottlenecks for comprehensive analysis, enhancing system robustness through Cas protein engineering and optimized reagents, developing fully integrated, sample-to-answer microfluidic or lateral flow devices for user-friendly field deployment, and collaboratively establishing universally accepted validation guidelines, performance standards, and stringent QA/QC procedures. Furthermore, the urgent development of clear ethical guidelines governing the use of this highly sensitive technology, particularly concerning RNA data privacy and potential misuse, is imperative. This review systematically outlines the principles, forensic applications, current limitations, and future trajectories of CRISPR-RNA detection, with the authors’ conviction that focused efforts addressing these challenges will translate this technology into a cornerstone of next-generation forensic practice, driving unprecedented efficiency and innovation in field investigations and laboratory analysis to enhance justice delivery.