The technology developed for COVID-19 by researchers at the California Institute of Technology (Caltech) can also be used to create tests to identify other pathogens.

The study, which is detailed in a paper published in the journal ACS Infectious Diseases, was carried out in the lab of Niles Pierce, a professor of applied and computational mathematics and bioengineering and executive officer for biology and biological engineering, who said that the COVID-19 pandemic demonstrated the “difficulty of scaling diagnostics quickly to the level of the human population” and so we must be ready to act.

A significant challenge in instrument-free at-home COVID-19 testing is that SARS-CoV-2 (the virus that causes the disease) can be present in very low amounts in a given sample. Bits of the viral RNA genome present in a patient’s sample are used to generate multiple DNA copies in laboratory-based polymerase chain reaction (PCR) testing; yielding an amplified signal that can be detected more easily. Although the PCR test is the gold standard for identifying infections, lab-based PCR tests take a long time to complete and require costly equipment.

The advantage of at-home rapid tests, however, is that they don’t require any equipment. Instead, they use specially created antibodies to bind colored reporter molecules to any SARS-CoV-2 proteins found in the sample, producing an unamplified signal. When there is little to no virus present in the sample, the color’s brightness, or signal, is very weak or even undetectable. Even if a person tested positively for COVID-19, this could result in false-negative results.

Researchers from the Pierce lab have combined amplification techniques with the simplicity of at-home test in their most recent work. They accomplished this by using a technique known as hybridization chain reaction (HCR), which increases the signal of the reporter molecules. Every viral protein that is captured by the new test then develops a lengthy DNA tail.

Instead of encoding for anything biological, this DNA serves as a specially constructed scaffold to which a variety of eye-catching reporter molecules can attach, the researchers explained, adding that each viral particle emits a much “brighter” signal in this way. The amplified test was created using a clever engineering process so that each step happens in a disposable device about the size of a playing card without user input.

To release the tests on the market, the team intends to keep improving both tests and collaborate with business associates.

Source: https://www.caltech.edu/about/news/at-home-rapid-covid-test-sensitivity

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