Table 3.
Applications of the digital nucleic acid assay in detecting SARS-CoV-2
| Compartmentalization methods | Analyte | Amplification methods | Performance | Detecting methods | References |
|---|---|---|---|---|---|
| Crossflow/T-junction | SARS-CoV-2 ORF1ab, N and RNase P genes | RT-qPCR | 5 copies/test in 5 min | Fluorescent probes | [164] |
| Flow-focusing by QX200™ Droplet Digital™ PCR System, Bio-Rad (Pleasanton, California, U.S.) | SARS-CoV-2 ORF1ab, N and E genes | RT-qPCR | 2 copies/reaction in 4 h | TaqMan Hydrolysis probe and EvaGreen | [165] |
| Flow-focusing by QX200™ Droplet Digital™ PCR System | SARS-CoV-2 ORF1ab and N genes | RT-qPCR | 1.4 copies/reaction | TaqMan PCR reaction mixture | [157] |
| By head-flattened pipette tips | SARA-CoV-2 ORF1ab and N genes | RT-qPCR | 3.8 copies/reaction in 1.5 h | Thermo Scientific TaqMan 2019-nCoV Assay Kit v1 | [166] |
| Flow-focusing by QX200™ Droplet Digital™ PCR System | SARS-CoV-2 RdRp and RNase P genes | RT-PCR | 2.9 copies /reaction |
GeneFinder™ COVID-19 Plus RealAmp Kit, ELITech and Allplex™ 2019-nCoV Assay, Seegene |
[167] |
| SlipChip | SARS-CoV-2 NA extracted from the COVID-19 pseudo virus | LAMP | 344 copies/ml | LAMP fluorescent dye | [71] |
| Microwell arrays | Synthetic SARS-CoV-2 targets | CRISPR-Cas13-based SHERLOCK technology | 10 copies/ml | Single-stranded DNA fluorogenic reporters | [158] |
| By QuantStudio chips (ThermoFisher) with 0.7 nl digital reaction wells | SARS-CoV-2 N gene | CRISPR/Cas12a based RT-RPA | 1 GE/µl of SARS-CoV-2 RNA and 20 GE/µl of heat-inactivated SARS-CoV-2, qualitative detection in 15 min and quantitative detection in 30 min | Single-stranded DNA fluorogenic reporters | [169] |
RT-qPCR reverse-transcription quantitative polymerase chain reaction, LAMP loop-mediated isothermal amplification, RT-PCR reverse-transcription polymerase chain reaction, CRISPR clustered regularly interspaced short palindromic repeats, SHERLOCK specific high sensitivity enzymatic reporter unlocking, RT-RPA reverse-transcription recombinase polymerase amplification, GE genome equivalent, COVID-19 corona virus disease 2019, SARS-CoV-2 severe acute respiratory syndrome coronavirus 2