Integration of CRISPR/Cas with functional nucleic acids as versatile toolbox for non-nucleic acid target diagnostics: a review

Non-nucleic acid targets, consisting primarily of metal ions, organic small molecules and proteins. They act as important biomolecules or cell surface markers, supplying integrated and comprehensive bio-diagnostic information for the early diagnosis and treatment of diseases. Meanwhile, the analysis of non-nucleic acid targets also offers the foundation for individualized medicine and precision therapy. Therefore, a versatile platform for non-nucleic acid targets requires development. Clustered regularly interspaced short palindromic repeats-associated protein (CRISPR/Cas) systems is driving a revolution in medical diagnostics due to high base-resolution and isothermal signal amplification. Nevertheless, the majority of CRISPR/Cas settings reported currently are targeted for nucleic acids, leaving restricted usage to non-nucleic acid targets. This is owing to the lack of suitable signal recognition transduction elements for connecting CRISPR to non-nucleic acid targets. Functional nucleic acids (FNAs), comprising aptamers and nucleic acid enzymes, are of great concern to the biological and medical professions because of their specific target recognition and catalytic properties. As appropriate, functional recognition elements, FNAs can be integrated into CRISPR/Cas systems to exploit the powerful capabilities of both. This review emphasizes the technical tricks of integrating CRISPR/Cas systems and FNAs for non-nucleic acid targeting diagnostic applications. We first offer a general overview and the current state of research in diagnostics for CRISPR/Cas and FNAs, respectively, highlighting strengths and shortcomings. A categorical summary of non-nucleic acid-targeted diagnostics is provided, with a key emphasis on fundamental insights into the versatile non-nucleic acid-targeted diagnostic toolbox. We then review emerging diagnostic strategies based on CRISPR/Cas systems and FNAs that are fast, accurate and efficient in detecting non-nucleic acid targets. Finally, we identify the challenges that remain in this emerging field and look to the future of the field, expanding to the integration of nanomaterials, development of wearable devices and point-of-care testing.