Rapid detection of SARS-CoV-2 antigen based on IgG colloidal gold immunochromatographic strip

In December 2019, Wuhan, China, reported the first cases of pneumonia caused by a previously unknown coronavirus, subsequently designated SARS-CoV-2. This pathogen precipitated a global pandemic of coronavirus disease 2019 (COVID-19). The virus primarily transmits via aerosols, direct contact, and contaminated surfaces. Its high infectivity and rapid transmission have posed severe public health challenges on a global scale, emphasizing the essential need for precise and swift diagnostic techniques to effectively track and curb its transmission. To address this need, we designed a highly efficient approach, namely a colloidal gold immunochromatographic strip (CGICS) based on an IgG-mediated immunoassay, for the specific capture of the SARS-CoV-2 nucleocapsid (N) antigen. Evaluation of the assay's specificity with a panel of common respiratory viral pathogens revealed that the CGICS specifically recognized SARS-CoV-2, with no cross-reactivity observed against non-target viruses. In addition, limit-of-detection (LOD) assessments indicated that the minimum detectable concentration was 2 ng/mL, and agreement analysis experiments showed a concordance rate of 98%, demonstrating high specificity and sensitivity. The resulting CGICS was capable of detecting SARS-CoV-2 antigen within 5-15 min. This study provides a rapid diagnostic approach for early SARS-CoV-2 infection, offering significant implications for effective disease prevention, control, and clinical diagnosis.