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. 2021 Sep 8;11(9):1646. doi: 10.3390/diagnostics11091646

Figure 5.

Figure 5

Schematic diagram depicted the trans-cleavage activity of Cas13 enzyme. In the presence of SAR-CoV-2 virus, the RNA amplicon after RT-LAMP and T7 transcription was complemented to pre-designed crRNA (ribonucleoprotein complex, Cas13 + crRNA + amplicon). As a result, the Cas13 enzyme was activated to cleave the reporter probes, and the lateral flow assay (IFA) showed both a control (C) and a test (T) line, indicating a positive COVID-19 result. In absence of SAR-CoV-2 virus, there was no amplification of target site and binding to crRNA. Thus, Cas13 enzyme remain inactivated, and the reporter probes were not cleaved. The LFA showed only control line, indicating negative COVID-19 result. The un-cleaved reporter molecules are captured at the first detection line (control line), whereas indiscriminate Cas13 cleavage activity generates a signal at the second detection line (test line).