This colorized scanning electron microscope image shows SARS-CoV-2 (round blue objects), the virus that causes COVID-19, emerging from the surface of cells cultured in the lab. [Image courtesy of National Institute of Allergy and Infectious Diseases]
The probes, called “positive controls,” are made from virus-like particles and are stable and easy to manufacture, according to a news release. The researchers at UCSD believe the positive controls can improve the accuracy of the rapid COVID-19 diagnostics that are used outside the lab and have been the subject of scrutiny due to issues with accuracy when compared to lab-based PCR tests.
“Our goal is to make an impact not necessarily in the hospital, where you have state-of-the-art facilities, but in low-resource, underserved areas that may not have the sophisticated infrastructure or trained personnel,” UCSD Jacobs School of Engineering professor of nanoengineering Nicole Steinmetz said in a news release.
According to the researchers, positive controls that are primarily used to validate today’s COVID-19 tests are naked synthetic RNAs, plasmids or RNA samples from infected patients. However, RNA and plasmids aren’t stable like viral particles, the engineers said, with degradation and the requirement of refrigeration making them inconvenient and costly.
The researchers published a paper in ACS Nano last week that reported the ability to create stable positive controls for COVID-19 tests that can be stored for a week at temperatures reaching 40 C (104 F) and retain 70% of their activity even after one month of storage while passing detection as the novel coronavirus without being infectious.
One control was developed from plant virus nanoparticles, while the other was made from bacteriophage nanoparticles. Both were validated with clinical samples and, unlike positive controls currently used, can be used in all steps of a COVID-19 test, the researchers say.
As of now, the researchers have adapted their controls for use in the CDC-authorized RT-PCR test and are now working to adapt the controls for use in less complex diagnostic tests like the RT-LAMP that can be done on the spot and provide results right away.
“It’s a relatively simple nanotechnology approach to make low-tech assays more accurate,” Steinmetz said. “This could help break down some of the barriers to mass testing of underserved populations in the U.S. and across the world.”
