Antibody and Aptamer-Based Magnetic-Graphene Oxide Desorption (M-GOD) Quantum Dot Assays for Rapid and Sensitive Detection of SAR-CoV-2.

Rapid detection of respiratory diseases using a noninvasive bind-and-detect breath test could shift the future of rapid diagnostics. Commercially available biotinylated anti-SARS-CoV-2 spike (S) protein antibody was conjugated to streptavidin-coated quantum dots, purified, and adsorbed onto magnetic-graphene oxide (M-GO) flakes to quench the conjugate. When inactivated SARS-CoV-2 was added at increasing levels, the antibody-quantum dot conjugates desorbed from the M-GO as a function of virus concentration with an apparent limit of detection ~ 9,600 inactivated virus particles within 2-5 min in phosphate-buffered saline (PBS) plus 10 mM Mg2+ assessed by a spectrofluorometer. A similar fluorescence response was obtained using a published biotinylated DNA aptamer sequence designated MSA52 and inactivated SARS-CoV-2 in PBS plus 5 mM Mg2+. Concentrations of Mg2+ greater than 5 mM diminished the aptamer magnetic-graphene oxide desorption (M-GOD) assay performance, perhaps by altering the aptamer's 3-dimensional conformation and ability to bind the virus. As reported previously, the MSA52 aptamer assay demonstrated reasonable specificity for variants of SARS-CoV-2 and significantly less intense detection of inactivated Influenza A and Respiratory Syncytial Virus (RSV) in the M-GOD assay format. This rapid and sensitive detection of inactivated SARS-CoV-2 in clear PBS buffer bodes well for the ultimate goal of rapid homogeneous bind-and-detect detection of COVID and other viral respiratory pathogens in human breath condensates and other easily accessible body fluids.