New home COVID test can detect specific variants in just an hour

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New home coronavirus test developed by scientists at Massachusetts Institute of Technology (MIT), Harvard University and Boston area hospitals can tell users within an hour if they are infected with COVID and with what variant they are infected.

Most of the home tests currently available are rapid antigen tests, which are not as reliable as the PCR tests available at official health and testing centers. Testing for specific variants of the novel coronavirus is even less accessible, with global lack of access to genetic testing causing delays in tracking and responding to new variants around the world.

Variant tracking has become a key part of the response to the coronavirus pandemic, as new variants have been found to increase infectivity and resistance to vaccines, a recent Israeli study finding that the Pfizer coronavirus vaccine does not was only 40% effective against symptomatic cases of the disease. virus.

“The ability to detect and track these variants is essential for effective public health, but unfortunately variants are currently only diagnosed by nucleic acid sequencing at specialized epidemiological centers which are rare even in resource-rich countries.” said Helena de Puig, lead author on the study of the new device and post-doctoral fellow at Harvard University’s Wyss Institute for Biologically Inspired Engineering, according to the MIT press office.

The new SHERLOCK Minimal Instrumentation Device (miSHERLOCK) aims to address these issues by providing an easy-to-use and affordable test that uses a saliva sample to test for virus and specific variants and can be assembled using a printer. 3D and commonly available components. for around $ 15 (this price could drop to $ 2-3 if the device is mass produced).

Scientists pointed out that although saliva is not commonly used for coronavirus testing, several studies have shown it to be as reliable as nasal and oral swabs. Israeli research published last month found that saliva tests work the same as swabs. SARS-CoV-19 has also been found to be detectable in saliva for more days after infection.

The miSHERLOCK device uses a CRISPR-based technology called “Specific High Sensitivity Enzymatic Unlocking” (SHERLOCK), which was developed by Jim Collins, lead author of the article and senior faculty member at the Wyss Institute for Biologically Inspired Engineering at Harvard University.

SHERLOCK technology uses CRISPR’s “molecular scissors” to find viral RNA in saliva samples by cutting RNA or DNA at specific locations. The technology also cuts single-stranded DNA probes to produce a fluorescent signal.

The team was to include a pretreatment step that deactivates enzymes called salivary nucleases, which destroy nucleic acids such as RNA, according to the MIT News Office. Once the sample enters the device, the device uses heat and two chemical reagents to inactivate nucleases. The viral RNA is then extracted and concentrated by passing the saliva through a membrane that traps RNA on its surface.

The battery powered test set consists of two chambers: a heated sample preparation chamber and an unheated reaction chamber.

Using the test device is a simple three-step process. First, the user spits into the sample preparation chamber, turns on the heater, and waits three to six minutes for the saliva to pass through the filter. The user then removes the filter and transfers it to the reaction chamber, pushes a plunger which deposits the filter in the chamber and pierces a water reservoir to activate the SHERLOCK reaction.

Less than an hour later, the user verifies that he can see a fluorescent signal through a window in the reaction chamber and can then use an accompanying smartphone app to analyze the pixels to provide a diagnosis. positive or negative clear.

“Our goal was to create a fully self-contained diagnosis that requires no other equipment,” Xiao Tan, clinical researcher at the Wyss Institute and gastroenterology instructor at Massachusetts General Hospital, told MIT News Office. “Basically the patient spits into this device and then you push a plunger and you get a response an hour later. “

The device is modular and can contain up to four modules which each search for a different target RNA sequence. The original module includes RNA guide strands that detect any strain of the novel coronavirus, while the other modules can include guide strands to search for specific variants.

Co-first author Devora Najjar, research assistant at MIT Media Lab and Collins Lab, explained that modules for new variants could be created in about two weeks, which would allow rapid development of tests for new variants.

The device was tested on saliva samples from 27 COVID-19 patients and 21 healthy patients and correctly identified patients positive for coronavirus 96% of the time and patients negative for coronavirus 95% of the time, according to the Wyss Institute.

The device was also tested on its performance by identifying the Alpha, Beta and Gamma variants of SARS-CoV-19 (the Delta variant was not widespread at the start of the study) and the device was able to effectively identify the variants.

“When the miSHERLOCK project started, there was almost no monitoring for SARS-CoV-2 variants. We knew that variant tracking was going to be extremely important when assessing the long-term effects of COVID-19 on local and global communities, so we pushed ourselves to create a truly decentralized, flexible, and diagnostic platform. user-friendly, ”Collins said in a press release from the Wyss Institute, noting that the team is“ delighted to work with industrial partners to make it commercially available ”.



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