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

We have demonstrated a portable chemiluminescent microfluidic ELISA system that is able to conduct sensitive detection and quantification of SARS-CoV-2-related biomarkers in only 15-20 minutes using micro-liter sized sample volumes. The LLOD of 2 ng/mL for IgG in serum was achieved using the humanized chimeric antibodies as the model system. We also successfully characterized different antibodies and identified an antibody candidate, D006, which can be used as the calibration antibody for quantitative evaluation of anti-SARS-CoV-2 S1 IgG. This approach can also be extended to evaluation of therapeutic convalescent plasma. Furthermore, we demonstrated sensitive detection of SARS-CoV-2 S1 protein (antigen) with the LLOD of 0.4 ng/mL. Finally, we showed that our technology can be used as an alternative approach for rapid (8.5 minutes) screening and validation of monoclonal anti-S1 antibodies. Our method requires only tens of nanograms, which is several orders of magnitude smaller than used traditional label-free methods (such as BLI and SPR), and will be useful in screening and selection of high affinity therapeutic neutralization antibodies and research-use antibodies 23, 27-29 .