Fig. 5: SARS-CoV-2 detection in clinical samples.

a, Normalized sensor response for nasopharyngeal swab samples (n = 11) from healthy volunteers (1–7) and COVID-19-positive samples from walk-in patients (8–11). Cycle threshold values from RT-PCR are indicated above the positive samples. b, Sensor response for a tenfold dilution series of nasal swab sample number 8, along with RT-PCR results after RNA extraction from the same diluted samples (values above the bars). ND, not detected. The error bars in a and b indicate the s.d. measured from two gate electrodes combined with three channels. All positive samples were also measured using two GFP nanobody gate electrodes each. c, Average sensor response for saliva samples (n = 13) taken from healthy volunteers (12–17) and outpatients who had recently tested positive for COVID-19 (18–24). RT-qPCR was performed on each sample and the viral copy numbers in the 5 µl sample volume are indicated above the bars. The error bars show the s.e.m. from three gate electrodes measured on one channel. Measurements with one GFP nanobody gate per COVID-19-positive sample served as an additional negative control. As before, the normalized response was calculated as \({\rm{normalized}} \, {\rm{response}} = (|I_{\mathrm{D}} - I_0|)/I_0\) (the current change normalized to the baseline signal). K, thousand; M, million.