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Table 3 Applications of the digital nucleic acid assay in detecting SARS-CoV-2

From: Microfluidics-based strategies for molecular diagnostics of infectious diseases

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
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]
  1. 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