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Scientists at Harvard and MIT have developed a low-cost CRISPR-based diagnostic test that allows users to test themselves for the SARS-CoV-2 virus and its multiple variants using a saliva sample at home , without any additional instrument needed.
The device, called the minimally instrumented SHERLOCK (miSHERLOCK), is easy to use and delivers results that can be read and verified on a smartphone app within an hour, the researchers said.
It was able to distinguish three different variants of SARS-CoV-2 in the experiments and can be quickly reconfigured to detect additional variants like Delta, they said.
The device, described in the journal Science Advances, can be assembled using a 3D printer and commonly available components for around $ 15, and reusing the hardware cuts the cost of individual tests to $ 6 each.
“MiSHERLOCK eliminates the need to transport patient samples to a centralized testing site and dramatically simplifies sample preparation steps, giving patients and physicians a faster and more accurate picture of individual and community health, which is essential during an evolving pandemic, ”said Helena de Puig, postdoctoral fellow at Harvard University and the Massachusetts Institute of Technology (MIT).
The researcher used a CRISPR-based technology called ‘Specific High Sensitivity Enzyme Unlocking’ (SHERLOCK).
CRISPR technology is a simple but powerful tool for editing genomes. It allows researchers to easily modify DNA sequences and alter the function of genes.
SHERLOCK uses the molecular scissors of CRISPR – an enzyme called Cas12a – to cut DNA or RNA at specific places.
The researchers used SHERLOCK to cut SARS-CoV-2 RNA into a specific region of a gene called a nucleoprotein that is conserved in several variants of the virus.
When the molecular scissors bind and successfully cut the nucleoprotein gene, single-stranded DNA probes are also cut, producing a fluorescent signal.
They also created additional SHERLOCK assays designed to target a panel of viral mutations in advanced protein sequences that represent three genetic variants of SARS-CoV-2: Alpha, Beta and Gamma.
The spike protein is used by the SARS-CoV-2 virus to infect and enter human cells.
The team used saliva samples rather than nasopharyngeal swabs for the test because it is easier for users to collect saliva, and studies have shown that SARS-CoV-2 is detectable in saliva for a period of time. greater number of days after infection.
The researchers tested their diagnostic device using clinical saliva samples from 27 COVID-19 patients and 21 healthy patients.
They found that miSHERLOCK correctly identified COVID-19 positive patients 96% of the time and patients without the disease 95% of the time.
The researchers also tested its performance against the Alpha, Beta, and Gamma variants of SARS-CoV-2 by spiking healthy human saliva with full synthetic viral RNA containing mutations representing each variant.
They found the device to be effective over a range of viral RNA concentrations.
One of the advantages of miSHERLOCK is that it is completely modular. The device itself is separate from the tests, so you can plug in different tests for the specific sequence of RNA or DNA you are trying to detect, ”said Devora Najjar, research assistant at MIT Media Lab.
The team created their device with low-resource environments in mind, as the pandemic shed light on the vast inequalities in access to healthcare that exist between different parts of the world.
(This story was not edited by Devdiscourse staff and is auto-generated from a syndicated feed.)
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