Gold nanoparticle conjugate-based lateral flow immunoassay (LFIA) for rapid detection of RBD antigen of SARS CoV-2 in clinical samples using smartphone-based application.

COVID-19 pandemic has emphasized the need for the development of a rapid diagnostic device for the effective treatment of COVID-19 for its mitigation. Lateral flow immunoassay (LFIA) belongs to a class of diagnostic devices, which has the benefit of providing quick results, easy to handle, low cost, and on-site detection. So far, several LFIA has been developed for the detection of infectious SARS-CoV-2, however, only few of them are antigen-based. Here, we present an antibody labeled gold-nanoparticle (AuNPs) based lateral flow immunoassay (AuNPs-LFIA) for the detection of Receptor Binding Domain (RBD) of SARS CoV-2. For this, RBD antibody (Ab) of SARS CoV-2 was conjugated with the AuNPs which served as a detecting probe. The fabricated LFIA strip was optimized for different parameters such as membrane pore size, blocking conditions, antibody coating concentration, and conjugate incubation. The optimized LFIA strips were validated in spiked buffer samples and the optimal limit of detection was found to be 1 ng/mL, which was confirmed by smartphone-based application. Moreover, the developed AuNPs-LFIA strips effectively detected RBD antigen (Ag) in 100 clinical samples with 93% sensitivity in clinical samples if compared with gold standard (RT-PCR). The fabricated LFIA are reported to have storage stability of up to 21 days at 4˚C and RT, hence, can be used as a portable, cost-effective diagnostic device for rapid detection of SARS-CoV-2. This article is protected by copyright. All rights reserved.