Early Detection of SARS-CoV-2 Seroconversion in Humans with Aggregation-Induced Near-Infrared Emission Nanoparticle-Labeled Lateral Flow Immunoassay

An outbreak of coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 SARS-CoV-2) poses great threats to human health and the international economy. To reduce large-scale infection and transmission risk of SARS-CoV-2, a simple, rapid, and sensitive serological diagnostic method is urgently needed. Herein, an aggregation-induced emission (AIE) nanoparticle (AIE(810)NP, lambda(em) = 810 nm)-labeled lateral flow immunoassay was designed for early detection of immunoglobulin M (IgM) and immunoglobulin G (IgG) against SARS-CoV-2 in clinical serum samples. Using a near-infrared (NIR) AIE nanoparticle as the fluorescent reporter (Delta lambda = 145 nm), the autofluor-escence from the nitrocellulose membrane and biosample and the excitation background noise were effectively eliminated. After optimization, the limit of detection of IgM and IgG is 0.236 and 0.125 mu g mL(-1), respectively, commensurate with that of the enzyme-linked immunosorbent assay (ELISA) (0.040 and 0.039 mu g mL(-1)). The sensitivity of the proposed ALE(810)NP-based test strip for detecting IgM and IgG is 78 and 95% (172 serum samples), commensurate with that of ELISA (85 and 95%) and better than that of a commercial colloidal gold nanoparticle (AuNP)-based test strip (41 and 85%). Importantly, the time of detecting IgM or IgG with an AIE(810)NP-based test strip in sequential clinical samples is 1-7 days after symptom onset, which is significantly earlier than that with a AuNP-based test strip (8-15 days). Therefore, the NIR-emissive AIE nanoparticle-labeled lateral flow immunoassay holds great potential for early detection of IgM and IgG in a seroconversion window period.

Automated summary

A new serological diagnostic method was designed for early detection of COVID-19 using AIE nanoparticles. The method showed comparable or higher sensitivity to ELISA and outperformed a commercial colloidal gold nanoparticle test strip. Early detection of IgM and IgG was achieved within 1-7 days of symptom onset with the AIE nanoparticle-based test strip.