Improved detection sensitivity of an antigen test for SARS-CoV-2 nucleocapsid proteins with Thio-NAD cycling

Yuta Kyosei, Mayuri Namba, Sou Yamura, Satoshi Watabe, Teruki Yoshimura, Tadahiro Sasaki, Tatsuo Shioda, Etsuro Ito*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


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

Original languageEnglish
Pages (from-to)1332
Number of pages1
JournalBiological and Pharmaceutical Bulletin
Issue number9
Publication statusPublished - 2021 Sept


  • Antigen test
  • Coronavirus disease 2019
  • Nucleocapsid protein
  • Severe acute respiratory syndrome coronavirus 2
  • Thionicotinamide-adenine dinucleotide cycling
  • Ultrasensitivity

ASJC Scopus subject areas

  • Pharmacology
  • Pharmaceutical Science


Dive into the research topics of 'Improved detection sensitivity of an antigen test for SARS-CoV-2 nucleocapsid proteins with Thio-NAD cycling'. Together they form a unique fingerprint.

Cite this