Journal: Biosensors & Bioelectronics

Article Title: A novel rapid detection for SARS-CoV-2 spike 1 antigens using human angiotensin converting enzyme 2 (ACE2)

doi: 10.1016/j.bios.2020.112715

Figure Lengend Snippet: Laboratory confirmation of ACE2-based LFIA using clinical samples a) Schematic diagram of COVID-19 test using ACE2-based LFIA. A nasopharyngeal swab from the COVID-19 patient is placed into the UTM. 50 μL of UTM containing the SARS-CoV-2 is mixed with running buffer in a 1:1 (v/v) ratio, and 100 μL of mixed solution is loaded into the LFIA device. After 20 min, the line intensity of the LFIA strip is semi-quantified by the portable analyzer. b) Results of ACE2-based LFA for the detection sensitivity of cultured SARS-CoV-2. Serially diluted virus concentrates (concentration range: 1.07 × 10 8 copies/mL to 5.35 × 10 6 copies/mL) were tested. After 20 min, the LFIA strip was taken with a smartphone and scanned with an image analyzer. The line intensities of the test and control lines were converted to peak histograms. Also, the intensity of the test lines was measured by a portable line analyzer (I L : line intensity of test line). Furthermore, human coronavirus (OC43) was tested as a negative control. c) Bar graph of intensities for test lines measured by the portable analyzer. The limit of detection (LOD) was determined by the mean value of negative controls (0 copies/mL of SARS-CoV-2) plus three times the standard deviation. d) Laboratory confirmation of ACE2-based LFIA compared to the RT-qPCR using clinical samples. i) Nasopharyngeal swab samples of COVID-19 patients (n = 4) and healthy subjects (n = 4) were tested both ACE2-based LFIA and RT-qPCR. Sensitivity was determined by the number of true positive samples divided by the number of positive samples tested. Moreover, specificity was determined by the number of true negative samples divide by the number of negative samples tested. ii) RT-qPCR results for the detection of the SARS-CoV-2 specific gene (Env gene). C t value and their correspondent viral load in the clinical samples were evaluated. e) Results of ACE2-based LFIA on laboratory confirmation using clinical COVID-19 patient samples. Twenty minutes after sample loading, the test line intensities of the LFIA strips were measured with a portable line analyzer. The limit of detection (LOD) was determined by the mean value of negative controls (healthy control) plus three times the standard deviation.

Article Snippet: Moreover, nasopharyngeal swab samples from healthy subjects were purchased from LEE Biosolutions (Cat. No. 991-31-NC, MO, USA).

Techniques: Stripping Membranes, Cell Culture, Virus, Concentration Assay, Control, Negative Control, Standard Deviation, Quantitative RT-PCR