Tetra-primer ARMS-PCR combined with dual-color fluorescent lateral flow assay for the discrimination of SARS-CoV-2 and its mutations with a handheld wireless reader

Several virulent variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have emerged along with the spread of this virus throughout the population. Some variants can exhibit increased transmissibility and reduced immune neutralization reactivity. These changes are deeply concerning issues that may hinder the ongoing effort of epidemic control measures, especially mass vaccination campaigns. The accurate discrimination of SARS-CoV-2 and its emerging variants is essential to contain the coronavirus disease 2019 pandemic. Herein, we report a low-cost, facile, and highly sensitive diagnostic platform that can simultaneously distinguish wild-type (WT) SARS-CoV-2 and its two mutations, namely, D614G and N501Y, within 2 h. WT or mutant (M) nucleic acid fragments at each allelic locus were selectively amplified by the tetra-primer amplification refractory mutation system (ARMS)-PCR assay. Allele-specific amplicons were simultaneously detected by two test lines on a quantum dot nanobead (QB)-based dual-color fluorescent test strip, which could be interpreted by the naked eye or by a home-made fluorescent strip readout device that was wirelessly connected to a smartphone for quantitative data analysis and result presentation. The WT and M viruses were indicated and were strictly discriminated by the presence of a green or red band on test line 1 for the D614G site and test line 2 for the N501Y site. The limits of detection (LODs) for the WT and M D614G were estimated as 78.91 and 33.53 copies per mu L, respectively. This assay was also modified for the simultaneous detection of the N and ORF1ab genes of SARS-CoV-2 with LODs of 1.90 and 6.07 copies per mu L, respectively. The proposed platform can provide a simple, accurate, and affordable diagnostic approach for the screening of SARS-CoV-2 and its variants of concern even in resource-limited settings.

Automated summary

A low-cost and highly sensitive diagnostic platform is reported, which can simultaneously distinguish wild-type (WT) SARS-CoV-2 and its two mutations within 2 hours. The platform utilizes PCR amplification and a dual-color fluorescent test strip to detect the specific nucleic acid fragments, with results interpreted by the naked eye or a smartphone-connected device. This method provides a simple, accurate, and affordable approach for screening SARS-CoV-2 and its variants, even in resource-limited settings.