The diagnostic test requires a cell phone camera and a small darkened box. (Photo courtesy of Daniel Fletcher)

In a major scientific breakthrough that brings futuristic vision into a reality, a mobile phone-based device allows for portable and sensitive read-out of the assay. Its like putting your clinical test sample in a device, and getting a read-out on your smartphone in 15 to 30 minutes and tells you if you are infected with the COVID-19 virus or not.

In a new study published in the scientific journal Cell, the team from Gladstone, UC Berkeley, and UCSF has outlined the technology for a CRISPR-based test for COVID-19 that uses a smartphone camera to provide accurate results in under 30 minutes.

The technique was designed in collaboration with UC Berkeley bioengineer Daniel Fletcher, PhD, as well as Jennifer Doudna, PhD, who recently won the 2020 Nobel Prize in Chemistry for co-discovering CRISPR-Cas genome editing, the technology that underlies this work.

Current COVID-19 tests use a method called quantitative PCR -- the gold standard of testing. However, one of the issues with using this technique to test for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is that it requires DNA. Coronavirus is an RNA virus, which means that to use the PCR approach, the viral RNA must first be converted to DNA. 

Mobile Phone Microscopy

To demonstrate that SARS-CoV-2 screening with Cas13a would be possible outside of laboratory settings, the team of scientists, from Gladstone, UC Berkeley, and UCSF, designed a mobile phone-based fluorescence microscope and reaction chamber to quantify the fluorescent signal generated by the Cas13a direct detection assay. 

Cas13a is an outlier in the CRISPR tech world because it targets RNA, not DNA

The goal was to show that mass-produced consumer electronics, rather than specialized laboratory equipment, are sufficient to capture the small fluorescent signals generated by Cas13a direct detection. Interestingly, we found that our device was approximately an order of magnitude more sensitive than the plate reader used in the development of this assay due to reduced measurement noise and the ability to collect more time points, which decreased the uncertainty in slope estimations and therefore enabled us to distinguish smaller slopes relative to the control.

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