Fig. 4.

Evaluation of dWS-CRISPR assay for SARS-CoV-2 detection. (a) Endpoint fluorescence micrographs of the QuantStudio digital chip for the specificity detection of the dWS-CRISPR assays. SARS-CoV-2 PC, SARS-CoV control, MERS-CoV control, and Hs_RPP30 PC were from Integrated DNA Technologies. (b) Endpoint fluorescence micrographs of the chip for the dWS-CRISPR assays testing various concentrations of SARS-CoV-2 RNA within 90-min incubation at 52 °C. (c) The linear relationship between percentage of positive spots (Y) and concentration of targets (X). The blue frame shows the enlarged view of low concentration range from 5 × 10⁰ to 5 × 10⁴ copies/μl. For each concentration's testing, total positive spots in all the six micrographs were used and three chips were taken to run three independent assays (n = 3). Error bars represent the means ± s.d. from replicates. (d) Heat map displaying the determined RNA concentration by RT-qPCR and dWS-CRISPR for detecting SARS-CoV-2 RNA extracted from 32 clinical swab samples (Swab S1–S32) and three saliva samples (Saliva S1–S3). The presented concentrations are the average values in three independent assays. Blank means SARS-CoV-2 negative. PC, SARS-CoV-2-positive control sample. NC, SARS-CoV-2-negative control sample. NTC, non-template control. Each micrograph is a representative of six distinct regions taken to cover about 2809 microreactions. Scale bars are 300 μm. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)