Chemical additives-enhanced CRISPR/Cas12a-based RNA detection.

The CRISPR/Cas12a system has revolutionized molecular diagnostics due to its RNA-guided trans-cleavage activity, enabling programmable and highly accurate nucleic acid detection. However, most Cas12a-based assays are optimized for DNA targets, while direct RNA detection constrained by limited sensitivity, typically at the nanomolar level. Existing strategies to improve the performance of RNA analysis often rely on additional DNA activators or complex auxiliary systems. Here, we report a simple yet effective chemical additive-based strategy that overcomes these limitations. This chemical additives-enhanced CRISPR/Cas12a-based RNA detection (CARD) enables femtomolar-level RNA detection using only a single crRNA, without the need for DNA activators, reverse transcription, or strand-displacement reactions. Notably, this approach can be adapted to single-stranded DNA, enabling ssDNA detection at attomolar levels. Collectively, CARD provides a straightforward, amplification-free, and highly sensitive diagnostic framework that might be readily extended to other CRISPR/Cas systems for ultrasensitive nucleic acid diagnostics.