Fluorescence‐Quenching Lateral Flow Immunoassay for “Turn‐On” and Sensitive Detection of Anti‐SARS‐Cov‐2 Neutralizing Antibodies in Human Serum

Abstract The titer of anti‐severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) neutralizing antibodies (NAbs) in the human body is an essential reference for evaluating the acquired protective immunity and resistance to SARS‐CoV‐2 infection. In this study, a fluorescence‐quenching lateral flow immunoassay (FQ‐LFIA) is established for quantitative detection of anti‐SARS‐CoV‐2 NAbs in the sera of individuals who are vaccinated or infected within 10 min. The ultrabright aggregation‐induced emission properties encapsulated in nanoparticles, AIE 490 NP, are applied in the established FQ‐LFIA with gold nanoparticles to achieve a fluorescence “turn‐on” competitive immunoassay. Under optimized conditions, the FQ‐LFIA quantitatively detected 103 positive and 50 negative human serum samples with a limit of detection (LoD) of 1.29 IU mL −1 . A strong correlation is present with the conventional pseudovirus‐based virus neutralization test ( R 2 = 0.9796, P < 0.0001). In contrast, the traditional LFIA with a “turn‐off” mode can only achieve a LoD of 11.06 IU mL −1 . The FQ‐LFIA showed excellent sensitivity to anti‐SARS‐CoV‐2 NAbs. The intra‐ and inter‐assay precisions of the established method are below 15%. The established FQ‐LFIA has promising potential as a rapid and quantitative method for detecting anti‐SARS‐CoV‐2 NAbs. FQ‐LFIA can also be used to detect various biomarkers.