Development of RNA-Based Assay for Rapid Detection of SARS-CoV-2 in Clinical Samples

The ongoing spread of pandemic coronavirus disease-19 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is of growing concern. Rapid diagnosis and management of SARS-CoV-2 are crucial for controlling the outbreak in the community. Here, we report the development of a first rapid-colorimetric assay capable of detecting SARS-CoV-2 in the human nasopharyngeal RNA sample in less than 30 min.

We utilized a nanomaterial-based optical sensing platform to detect RNA-dependent RNA polymerase gene of SARS-CoV-2, where the formation of oligo probe-target hybrid led to salt-induced aggregation and change in gold-colloid color from pink to blue visibility range. Accordingly, we found a change in colloid color from pink to blue in assay containing nasopharyngeal RNA sample from the subject with clinically diagnosed COVID-19. The colloid retained pink color when the test includes samples from COVID-19 negative subjects or human papillomavirus-infected women.

The results were validated using nasopharyngeal RNA samples from positive COVID-19 subjects (n = 136). Using real-time polymerase chain reaction as gold standard, the assay was found to have 85.29% sensitivity and 94.12% specificity. The optimized method has detection limit as little as 0.5 ng of SARS-CoV-2 RNA.

We found that the developed assay rapidly detects SARS-CoV-2 RNA in clinical samples in a cost-effective manner and would be useful in pandemic management by facilitating mass screening.