Single-walled carbon nanotubes-based RNA protection and extraction improves RT-qPCR sensitivity for SARS-CoV-2 detection

The false-negative result of nucleic acid testing is an important cause of continued spread of COVID-19, while SARS-CoV-2 RNA degradation during transportation and nucleic acid extraction can lead to false-negative results. Here, we investigated that single-walled carbon nanotubes (SCNTs) could protect RNA from degradation for at least 4 days at room temperature. By constructing magnetism-functionalized SCNTs (MSCNTs), we developed a method that enabled protection and simple extraction of SARS-CoV-2 RNA, and the RNA-bound MSCNTs can be directly used for reverse transcription polymerase chain reaction (RT-qPCR) detection. The experimental results showed that 1 μg of MSCNTs adsorbed up to 24 ng of RNA. Notably, the MSCNTs-based method for extracting SARS-CoV-2 RNA from simulated nasopharyngeal swabs and saliva samples with mean recovery rates of 103% and 106% improved the sensitivity of RT-qPCR detection by 8-32 fold in comparison to current common methods. This improvement was largely attributable to the protection of RNA, enabling increased RNA load for downstream assays.