Improved Detection Sensitivity of an Antigen Test for SARS-CoV-2 Nucleocapsid Proteins with Thio-NAD Cycling

Antigen tests for infectious diseases are inexpensive and easy-to-use, but the limit of detection (LOD) is generally higher than that PCR tests, which considered gold standard. In present study, we combined a sandwich enzyme-linked immunosorbent assay (ELISA) with thionicotinamide-adenine dinucleotide (thio-NAD) cycling to improve LOD antigen coronavirus disease 2019 (COVID-19). For recombinant nucleocapsid proteins severe acute respiratory syndrome 2 (SARS-CoV-2), our ELISA thio-NAD was 2.95 × 10?17 moles/assay. When UV-irradiated inactive SARS-CoV-2 used, minimum detectable virions corresponding 2.6 104 RNA copies/assay were obtained using cycling. The volume each test 100 µL. value smaller latest fluorescent immunoassay SARS-CoV-2, indicating validity system COVID-19 diagnosis.