Abstract
Simple, rapid, specific, and sensitive point-of-care detection methods are needed to contain the spread of SARS-CoV-2. CRISPR/Cas9-based lateral flow assays are emerging as a powerful alternative for COVID-19 diagnostics. Here, we developed Bio-SCAN (biotin-coupled specific CRISPR-based assay for nucleic acid detection) as an accurate pathogen detection platform that requires no sophisticated equipment or technical expertise. Bio-SCAN detects the SARS-CoV-2 genome in less than 1 h from sample collection to result. In the first step, the target nucleic acid sequence is isothermally amplified in 15 min via recombinase polymerase amplification before being precisely detected by biotin-labeled nuclease-dead SpCas9 (dCas9) on commercially available lateral flow strips. The resulting readout is visible to the naked eye. Compared to other CRISPR-Cas-based pathogen detection assays, Bio-SCAN requires no additional reporters, probes, enhancers, reagents, or sophisticated devices to interpret the results. Bio-SCAN is highly sensitive and successfully detected a clinically relevant level (4 copies/mu L) of synthetic SARS-CoV-2 RNA genome. Similarly, Bio-SCAN showed 100% negative and 96% positive predictive agreement with RT-qPCR results when using clinical samples (86 nasopharyngeal swab samples). Furthermore, incorporating variant-specific sgRNAs in the detection reaction allowed Bio-SCAN to efficiently distinguish between the alpha, beta, and delta SARS-CoV-2 variants. Also, our results confirmed that the Bio-SCAN reagents have a long shelf life and can be assembled locally in nonlaboratory and limited-resource settings. Furthermore, the Bio-SCAN platform is compatible with the nucleic acid quick extraction protocol. Our results highlight the potential of Bio-SCAN as a promising point-of-care diagnostic platform that can facilitate low-cost mass screening for SARS-CoV-2.