COVID-19 variants’ cross-reactivity on the paper microfluidic particle counting immunoassay

Sangsik Kim, Ciara Eades, Jeong Yeol Yoon

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


SARS-CoV-2 has mutated many times since the onset of the COVID-19 pandemic, and the omicron is currently the most dominant variant. Determining the specific strain of the virus is beneficial in providing proper care and containment of the disease. We have previously reported a novel method of counting the number of particle immunoagglutination on a paper microfluidic chip using a smartphone-based fluorescence microscope. A single-copy-level detection was demonstrated from clinical saline gargle samples. In this work, we further evaluated two different SARS-CoV-2 monoclonal antibodies to spike vs. nucleocapsid antigens for detecting omicron vs. delta and spike vs. nucleocapsid proteins. The SARS-CoV-2 monoclonal antibody to nucleocapsid proteins could distinguish omicron from delta variants and nucleocapsid from spike proteins. However, such distinction could not be found with the monoclonal antibody to spike proteins, despite the numerous mutations found in spike proteins among variants. This result may suggest a clue to the role of nucleocapsid proteins in recognizing different variants.

Original languageEnglish (US)
Pages (from-to)7957-7965
Number of pages9
JournalAnalytical and bioanalytical chemistry
Issue number28
StatePublished - Nov 2022


  • COVID-19
  • Cross-reactivity
  • Delta
  • Omicron
  • Paper microfluidic chip
  • Smartphone microscope

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry


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