ABSTRACT
Objective: To develop a catalytic hairpin assembly (CHA)-based fluorescent assay for the detection of the target RNA of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), so as to realize the rapid nucleic acid testing of SARS-CoV-2. Methods: A 24-nt segment of the SARS-CoV-2 nucleocapsid protein gene (N gene, NC_045512.2) was chosen as the target RNA and the hairpin motif 1 (H1) and hairpin motif 2 (H2) were designed based on the principle of CHA reaction. The H1 motif was labelled with a fluorophore group as well as a quencher group. When the target RNA was added to the hairpin motifs, CHA reaction was triggered at room temperature (25 â), which led to the amplification of fluorescence signal, thereby enabling the rapid detection of the target RNA. After the optimization of the hairpin motifs and the experimental conditions, the sensitivity and the specificity of the testing method were measured to evaluate its performance. Results: We successfully constructed a CHA-based fluorescent assay specifically for the target RNA of SARS-CoV-2. With this method, testing could be completed at room temperature within 30 min. This testing method exhibited excellent specificity and could be used to accurately distinguish the perfectly-matched target RNA from the target RNA with single-base mutations. In addition, the testing method demonstrated good sensitivity, with a detection limit of 50 pmol/L. Conclusion: The proposed assay enables the simple and rapid detection of the SARS-CoV-2 target RNA with excellent sensitivity and specificity, showing great promise for further optimization and subsequent clinical application for the rapid detection of SARS-CoV-2 nucleic acid.
Subject(s)
COVID-19 , SARS-CoV-2 , Humans , Sensitivity and Specificity , RNA , Nucleic Acid Amplification Techniques/methodsABSTRACT
Introduction: The cold chain conditions have been suggested to facilitate long-distance transmission of SARS-CoV-2, but it is unclear how viable the virus is on cold chain packaging materials. Methods: This study used the MHV-JHM strain of murine hepatitis virus as a model organism to investigate the viability of SARS-CoV-2 on foam, plastic, cardboard, and wood sheets at different temperatures (-40°C, -20°C, and 4°C). In addition, the ability of peracetic acid and sodium hypochlorite to eliminate the MHV-JHM on plastic and cardboard sheets were also evaluated. Results: The results indicate that MHV-JHM can survive on foam, plastic, or cardboard sheets for up to 28 days at -40°C and -20°C, and up to 14 days on foam and plastic surfaces at 4°C. Although viral nucleic acids were still detectable after storing at 4°C for 28 days, the corresponding virus titer was below the limit of quantification (LOQ). Discussion: The study highlights that a positive nucleic acid test result may not indicate that the virus is still viable, and confirms that peracetic acid and sodium hypochlorite can effectively eliminate MHV-JHM on packaging materials under cold chain conditions.
