Development of a concentration method for simple and sensitive detection of SARS-CoV-2 in saliva using a magnetic nanoparticle kit

Background: When diagnosing viral infections in humans and animals, the presence of virus in a sample in trace amounts that are below the analytical sensitivity of the detection system may cause false negative results and inaccurate diagnosis. We previously reported the development of a simple virion concentration technique using 12 ml large-volume samples that can dramatically improve diagnostic sensitivity by increasing analytical sensitivity by 100-fold over conventional methods. The present study was conducted to further improve the simplicity and versatility of this method. We constructed a simple and highly sensitive method for the detection of SARS-CoV-2 in human saliva after concentration using a magnetic nanoparticle conjugated with polyethylene glycol (PEG). Results: Performance of the method was evaluated by comparing a combination of automated nucleic acid extraction and RT-qPCR or triplex RT-LAM detection in a spiked sample of 20 ml saliva collected from healthy humans. The method theoretically achieved 300-fold concentration of spiked SARS-CoV-2 in saliva, enabling 10- to 1000-fold higher analytical sensitivity for detection compared to conventional RNA extraction methods. Conclusions: This newly developed method allows for easy and reliable concentration of the virion in less than 60 min, improving the analytical sensitivity of the SARS-CoV-2 test. Further, the method allows for easy and reliable enrichment of the virus in less than 60 min, improving the analytical sensitivity of the SARS-CoV-2 test. This method is easily used for highly sensitive virus detection from a variety of human oral fluid samples and may also be applied to rapid and labor-saving screening tests by pooling a large number of samples.