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Crop Biotech Update

COVID-19 Test Uses CRISPR and Smartphone Camera

December 9, 2020
The new COVID-19 test uses CRISPR gene-editing technology and a smartphone to provide a positive or negative test result and measure viral load. Illustration from Gladstone Institutes

A team of scientists at Gladstone Institutes, University of California, Berkeley (UC Berkeley), and the University of California, San Francisco (UCSF) has developed the technology for a CRISPR-based test for COVID-19 that uses a smartphone camera to provide accurate results in under 30 minutes. The Gladstone team led by Dr. Melanie Ott and Parinaz Fozouni worked with UC Berkeley bioengineer Dr. Daniel Fletcher and Dr. Jennifer Doudna, senior investigator at Gladstone, professor at UC Berkeley, president of the Innovative Genomics Institute, and investigator of the Howard Hughes Medical Institute.

Current COVID-19 tests quantitative PCR which is the gold standard of testing. However, this technique requires DNA. Coronavirus is an RNA virus, which means that to use the PCR approach, the viral RNA must first be converted to DNA. All CRISPR diagnostics to date require the conversion of viral RNA to DNA which is time-consuming and complex. In contrast, this novel approach skips all the conversion and amplification steps, using CRISPR to directly detect the viral RNA.

Instead of the well-known protein Cas9 which cleaves DNA, this new test uses the Cas13 protein which cleaves RNA. The Cas13 protein is combined with a reporter molecule that glows when cut and then mixed with a patient's nasal swab. The sample is placed in a device attached to a smartphone. If the sample contains RNA from SARS-CoV-2, Cas13 will be activated and will cut the reporter molecule, causing the emission of a fluorescent signal. Then, the smartphone camera, essentially converted into a microscope, can detect the fluorescence and report that a swab tested positive for the virus.

The scientists tested their device using patient samples and confirmed that it could provide a very fast turnaround time of results for samples with clinically relevant viral loads. In fact, the device accurately detected a set of positive samples in under 5 minutes. For samples with a low viral load, the device required up to 30 minutes to distinguish it from a negative test.

For more details, read the article on the Gladstone Institutes website.

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