Rapid and quantitative detection of COVID-19 markers in micro-liter sized samples

Xiaotian Tan; Cory Lin; Jie Zhang; Maung Kyaw Khaing Oo; Xudong Fan

In addition to anti-S1 IgG, S1 protein itself may also be a marker in the prognosis of COVID-19. It may appear in blood for the patients who develop coronavirus viremia and the people who receive certain types of coronavirus vaccines (especially subunit vaccines). Recent evidence indicates that the viral proteins may also exist in mucus samples such as the saliva. To detect the S1 protein, we employed a standard sandwich ELISA format, as illustrated in Fig. 3(A) , in which a monoclonal SARS-CoV-2/SARS-CoV S1 RBD-specific antibody (D001) was used as the capture antibody and another S1 RBD-specific antibody (D003) was used as the detection antibody SARS-CoV-2/SARS-CoV. To reduce the number of steps as well as the total assay time, we directly conjugated HRP molecules on the detection antibody. According to the protocol in Figure S2 (C), the entire assay was completed in 20 minutes.