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

Abstract

COVID-19 pandemic has caused tens of thousands of deaths and is now a severe threat to global health. Clinical practice has demonstrated that the SARS-CoV-2 S1 specific antibodies and viral antigens can be used as diagnostic and prognostic markers of COVID-19. However, the popular point-of-care biomarker detection technologies, such as the lateral-flow test strips, provide only yes/no information and have very limited sensitivities. Thus, it has a high false negative rate and cannot be used for the quantitative evaluation of patient's immune response. Conventional ELISA (enzyme-linked immunosorbent assay), on the other hand, can provide quantitative, accurate, and sensitive results, but it involves complicated and expensive instruments and long assay time. In addition, samples need to be sent to centralized labs, which significantly increases the turn-around time. Here, we present a microfluidic ELISA technology for rapid (15-20 minutes), quantitative, sensitive detection of SARS-CoV-2 biomarkers using SARS-CoV-2 specific IgG and viral antigen -S protein in serum. We also characterized various humanized monoclonal IgG, and identified a candidate with a high binding affinity towards SARS-CoV-2 S1 protein that can serve as the calibration standard of anti-SARS-CoV-2 S1 IgG in serological analyses. Furthermore, we demonstrated that our microfluidic ELISA platform can be used for rapid affinity evaluation of monoclonal anti-S1 antibodies. The microfluidic ELISA device is highly portable and requires less than 10 L of samples for each channel. Therefore, our technology will greatly facilitate rapid and quantitative analysis of COVID-19 patients and vaccine recipients at point-of-care.was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission.

Laboratory diagnosis of coronavirus disease-2019 (COVID-19)

“…In addition, Tan et al designed a microfluidic ELISA test for quantitative detection of SARS-CoV-2 S1 protein and anti-SARS-CoV-2 S1 IgG using humanized SARS-CoV-2 IgG and recombinant S1 protein, respectively. The lower LOD of 2 ng/mL for anti-SARS-CoV-2 S1 IgG and of 0.4 ng/mL for S1 antigen was achieved in serum [91]. These studies demonstrated high performance of analyzing SARS-CoV-2 specific antibodies and antigens in COVID-19 patients by microarray and microfluidic chip.…”

RAPPID: a platform of ratiometric bioluminescent sensors for homogeneous immunoassays

“…Regression analysis yielded a Pearson’s correlation coefficient ( r ) = 0.996. d , Schematic overview of RAPPID sensors for the detection of trimeric SARS-CoV-2 spike proteins. Recently discovered antibodies 43,44 targeting distinct binding epitopes of the immunogenic spike protein were used to generate sensors in either a heteropair or homopair setup. e , f , RAPPID response curves in response to increasing concentrations of monomeric spike protein ( e ) and native trimeric spike protein ( f ) using both the heteropair (gray) and homopair (red) configuration.…”

“…LB and SB were expressed as fusion proteins with the RBD, enabling detection of all RBD-targeting antibodies. g , Ratiometric sensor response curves for neutralizing antibody 47D11 (left) 44 , and commercially available anti-spike D001 (center) and D003 (right) 43 . Insets show sensor response at low target concentrations, which allowed calculation of the limit of detection, as indicated in the graphs.…”

“…Taken together, these results illustrate the potential of RAPPID for on-demand development of new biosensors as soon as antibodies become available, and the ability of the platform to distinguish between oligomeric states of proteins. Recently discovered antibodies 43,44 targeting distinct binding epitopes of the immunogenic spike protein were used to generate sensors in either a heteropair or homopair setup. e,f, RAPPID response curves in response to increasing concentrations of monomeric spike protein (e) and native trimeric spike protein (f) using both the heteropair (gray) and homopair (red) configuration.…”

Biomedical Science to Tackle the COVID-19 Pandemic: Current Status and Future Perspectives

“…To reduce the volume of the samples analyzed, Tan et al combined microfluidics and ELISA to detect IgG against different SARS-CoV-2 proteins in 10 µL serological samples within 15–20 min. However, the age of the used samples was not mentioned [ 190 , 191 ].…”