Illustration and TEM image of SARS-CoV-2 positive control made from plant virus-based nanoparticles (left) and bacteriophage nanoparticles (right). (Credit: Soo Khim Chan/ACS Nano)

Nanoengineers at the University of California San Diego have developed new and improved probes, known as positive controls, that could make it easier to validate rapid, point-of-care diagnostic tests for COVID-19 across the globe.

The positive controls, made from virus-like particles, are stable and easy to manufacture. Researchers say the controls have the potential to improve the accuracy of new COVID-19 tests that are simpler, faster, and cheaper, making it possible to expand testing outside the lab.

By packaging segments of RNA from the SARS-CoV-2 virus into virus-like particles, they can create positive controls for COVID-19 tests that are stable — they can be stored for a week at temperatures up to 40 °C (104 °F), and retain 70 percent of their activity even after one month of storage — and can pass detection as the novel coronavirus without being infectious.