Lateral flow immunoassay of Fe3O4@PMAA@IgG nanoprobe for quick detection of SARS-CoV-2 based on natural color.

In the context of the ongoing normalisation of the SARS-CoV-2, the number of patients infected with the new coronavirus remains high on an annual basis. It is therefore imperative that individuals have access to rapid and cost-effective diagnostic tests. Conventional diagnostic tests,such as Reverse Transcription-Quantitative Polymerase Chain Reaction(RT-QPCR), Enzyme-Linked Immunosorbent Assay(ELISA) are costly and cumbersome, impeding their application in single-sample detection. This study has developed a cost-effective lateral flow immunoassay that rivals the sensitivity and simplicity of ELISA and colloidal gold tests, facilitating rapid and affordable detection of SARS-CoV-2 antigen. The synthesis of Fe3O4 particles with a diameter of approximately 150 nm was initially conducted via a solvothermal method. Subsequently, the preparation of Fe3O4@PMAA particles with carboxyl groups, was undertaken through a reflux precipitation polymerization. Finally, the above particles were coupled with mouse anti-coronavirus SARS-CoV-2 N protein IgG by standard NHS/EDC methods to obtain Fe3O4@PMAA@IgG nanoprobe. This nanoprobe was then used as an immunoconjugate pad for the detection of the SARS-CoV-2 nucleoprotein. The nanoprobe-based method demonstrated significant advantages in cost-effectiveness and timeliness (with an assay duration of only 1 min), costing approximately $0.13 per sample. When used for SARS-CoV-2 antigen detection, this cost represents only 0.02% of that of RT-QPCR and 0.05% of that of ELISA.The detection limit of the lateral flow immunoassay is (0. 5 ng/mL).