Fig. 5.

Schematic approaches for the diagnosis to detect SARS-CoV-2 nucleic acid. (a) Detection based on CRISPR/Cas methodology: Upon activation of Cas proteins in the vicinity of target RNA sequences (blue), it splits the fluorophore-RNA-quencher reporter molecules. The detached fluorophore is detected via increase in fluorescence. (b) Sensors with RNA toehold switch which unfolds on sensing of target RNA sequences to further bind ribosomes. These ribosomes produce enzymes with messenger RNA (mRNA) sequences which thereby, convert substrate into colored product. (c) Multi-part nucleic acid (MNA)-based enzymes on sensing of target RNA sequence congregate and thereafter, splits the fluorophore-quenched reporter molecules [52] (Reproduced with permission from publisher)