Fig. 3.

Fundamental steps of various CRISPR based COVID-19 detection tests. (A) Collection of sample, transport in Viral transport medium and isolation of RNA (B) Conversion of RNA to cDNA by Reverse transcription. This amplification step could be conducted at isothermal conditions by following RT-RPA of RT-LAMP method. (C) Amplified nucleic acid of viral sample need to be identified by specific viral gene amplification. Conventional method (qRT PCR) utilizes viral gene specific primers to amplify the specific gene segment and further these segments detected by double strand intercalating SYBR dye or fluorescent probes. Recent advancements in CRISPR based diagnostics (CRISPR-Dx) enabled utilization of different Cas enzymes for detection with high sensitivity either from RNA (Cas-13 based detection) or from cDNA (Cas12, Cas9 based etc) followed by color reaction due to the cleavage of reporter probes by the activated Cas enzymes.