Rapid and Sensitive Detection of anti-SARS-CoV-2 IgG, Using Lanthanide-Doped Nanoparticles-Based Lateral Flow Immunoassay

Abstract

The outbreak of 2019 coronavirus disease has been a challenge for hospital laboratories because of the huge number of samples that must be tested for the presence of the causative pathogen, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Simple and rapid immunodiagnostic methods are urgently needed to identify positive cases. Here we report the development of a rapid and sensitive lateral flow immunoassay (LFIA) that uses lanthanide-doped polysterene nanoparticles (LNPs) to detect anti-SARV-CoV-2 IgG in human serum. A recombinant nucleocapsid phosphoprotein of SARS-CoV-2 was dispensed onto a nitrocellulose membrane to capture specific IgG. Mouse anti-human IgG antibody was labeled with self-assembled LNPs that served as a fluorescent reporter. A 100-μL aliquot of serum samples (1:1000 dilution) was used for this assay and the whole detection process took 10 min. The results of the validation experiment met the requirements for clinical diagnostic reagents. A value of 0.0666 was defined as the cutoff value by assaying 51 normal samples. We tested 7 samples that were positive by reversetranscription (RT-)PCR and 12 that were negative but clinically suspicious for the presence of anti-SARS-CoV-2 IgG. One of the negative samples was determined to be SARS-CoV-2 IgG positive, while the results for the other samples were consistent with those obtained by RT-PCR. Thus, this assay can achieve rapid and sensitive detection of anti-SARS-CoV-2 IgG in human serum and allow positive identification in suspicious cases; it can also be useful for monitoring the progression COVID-19 and evaluating patients' response to treatment.

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“…The second category includes serological and immunological tests that primarily focus on the detection of antibodies developed in individuals because of their exposure to the virus. 16 , 17 While these tests are rapid and require minimal equipment, their clinical utility to indicate COVID-19 infection is limited, as it may take several days to weeks after the onset of the symptoms for a patient to develop a detectable antibody response. 18 − 20 Hence, a highly sensitive diagnostic method with rapid and continuous monitoring of SARS-CoV-2 is required to obtain valued information that could support physicians in better treatment of COVID-19-related conditions.…”

Developments in biosensors for CoV detection and future trends

“…These tests are rapid (10–30 min), can be utilized directly by the patients but are more expensive for a large screening than normal ELISA tests and suffer from poor analytical sensitivity ( Carter et al, 2020 ). Chen and co-workers have recently presented a simple and rapid LFIA that uses lanthanide doped nanoparticles for detecting anti- SARS-CoV-2 IgG in human serum with high diagnostic accuracy ( Z. Chen et al, 2020 ).…”

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“…However, their results seem to be non-conclusive as a chemiluminescence LFIA gave very different results. Additionally, Chen et al devised another LFIA test using lanthanide-doped NPs as a signaling agent to detect SARS-CoV-2 IgG in human serum [ 228 ]. This assay proved to be rapid (10 min), sensitive, specific and reproducible.…”