Imagine swabbing your nostrils, putting the swab in a device, and getting a read- out on your phone in 15 to 30 minutes that tells you if you are infected with the Covid-19 virus. This has been the vision for a team of scientists at Gladstone Institutes, University of California, Berkeley (UC Berkeley), and University of California, San Francisco (UCSF). And now, they report a scientific breakthrough that brings them closer to making this vision a reality.
One of the major hurdles to combating the Covid-19 pandemic is the availability of mass rapid testing. Knowing who is infected would provide valuable insights about the potential spread and threat of the virus for policymakers and citizens alike.
Yet, people must often wait several days for their results, or even longer when there is a backlog in processing lab tests. And, the situation is worsened by the fact that most infected people have mild or no symptoms, yet still carry and spread the virus.
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.
“It has been an urgent task for the scientific community to not only increase testing, but also to provide new testing op- tions,” says Melanie Ott, MD, PhD, direc- tor of the Gladstone Institute of Virology and one of the leaders of the study. “The assay we developed could provide rapid, low-cost testing to help control the spread of COVID-19.”
The technique was designed in collaboration with UC Berkeley bioengineer Daniel Fletcher, PhD, as well as Jennifer Doudna, PhD, who is a senior investigator at Glad- stone, a professor at UC Berkeley, president of the Innovative Genomics Institute, and an investigator of the Howard Hughes Medical Institute. Doudna recently won the
2020 Nobel Prize in Chemistry for co-dis- covering CRISPR-Cas genome editing, the technology that underlies this work.
Not only can their new diagnostic test generate a positive or negative result, it also measures the viral load in a given sample.
“When coupled with repeated testing, measuring viral load could help deter- mine whether an infection is increasing or decreasing,” says Fletcher, who is also a Chan Zuckerberg Biohub Investigator. “Monitoring the course of a patient’s in- fection could help health care professionals estimate the stage of infection and predict, in real time, how long is likely
needed for recovery.”
“One reason we’re excited about CRIS-PR-based diagnostics is the potential for quick, accurate results at the point of need,” says Doudna. “This is especially helpful in places with limited access to testing, or when frequent, rapid testing is needed. It could eliminate a lot of the bottlenecks we’ve seen with Covid-19.” “What really makes this test unique is that it uses a one-step reaction to directly test the viral RNA, as opposed to the two-step process in traditional PCR tests,” says Dr Ott, who is also a professor in the Department of Medicine at UCSF. “The simpler chemistry, paired with the smart-phone camera, cuts down detection time and doesn’t require complex lab equipment. It also allows the test to yield quantitative measurements rather than simply a positive or negative result.”
The researchers also say that their as say could be adapted to a variety of mobile
phones, making the technology easily accessible. “We chose to use mobile phones as the basis for our detection device since they have intuitive user interfaces and highly
sensitive cameras that we can use to detect fluorescence,” explains Fletcher. “Mobile
phones are also mass-produced and cost-effective, demonstrating that specialized lab instruments aren’t necessary for this assay.”
When the scientists tested their device using patient samples, they 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.
Not only does the new CRISPR-based test offer a promising option for rapid testing, but by using a smartphone and avoiding the need for bulky lab equipment, it has the potential to become portable and eventually be made available for point-of- care or even at-home use. And, it could also be expanded to diagnose other respiratory viruses beyond SARS-CoV-2.
In addition, the high sensitivity of smart- phone cameras, together with their connectivity, GPS, and data-processing capabilities, have made them attractive tools for diagnosing disease in low-resource regions.
“We hope to develop our test into a device that could instantly upload results into cloud-based systems while maintain- ing patient privacy, which would be impor- tant for contact tracing and epidemiologic studies,” Dr Ott says. “This type of smart- phone-based diagnostic test could play a crucial role in controlling the current and future pandemics.”
Reference:
https://doi.org/10.1016/j.cell.2020.12.001
