Novel non-nucleic acid targets detection strategies based on CRISPR/Cas toolboxes: A review

Various non-nucleic acid targets (ions, small molecules, polysaccharides, peptides/proteins/enzymes, cells, transcription factors) are important biomarkers. They play important roles in environmental protection, food safety and medical diagnosis. Therefore, it is necessary to detect non-nucleic acid targets from various samples before the situation deteriorates. Derived from prokaryotic immune systems, CRISPR/Cas tools have exhibited great promise in the field of biosensing, in addition to the well-known gene-editing function. However, most reported CRISPR/Cas-based biosensors are for nucleic acid detection and the application of non-nucleic acid targets is still in its infancy. To fully explore the potential of CRISPR/Cas-based biosensing systems, it is of great significance to summarize the strategies and prospects of CRISPR/Cas toolboxes in non-nucleic acid targets recognition. In this review, we introduced CRISPR/Cas systems and their characteristics in the field of detection. The progress of detecting six non-nucleic acid targets was outlined and reviewed based on CRISPR/Cas systems coupled with biotransduction elements, including aptamers, DNAzymes, riboswitches, enzymatic reactions, transcription factors, antigen-antibody interactions, allosteric probes, in vitro transcription processes, steric hindrance effectors, etc. The development challenges and prospects in this field were also put forward. As such, this comprehensive review would provide valuable information for the expansion of the powerful CRISPR/Cas toolboxes into multiple detection fields.