During the pandemic, infectious disease specialists and frontline health workers ordered a faster, cheaper, and more reliable COVID-19 test. Now, taking advantage of the so-called “on-chip lab” technology and advanced gene editing technique called CRISPR, researchers at Stanford have created a highly automated device that can determine presence of coronavirus as early as half an hour. .
Lead author of the study, Juan G. Santiago, Professor of Mechanical Engineering at the Charles Lee Powell Foundation, said: “A microlab is a microchip about half the size of a credit card that contains a complex network of channels smaller than the width of a human hair. engineering at Stanford and a specialist in microfluidics, a field devoted to small-scale control of liquids and molecules using chips.
The new COVID-19 test is detailed in a study published Nov. 4 in the journal. Proceedings of the National Academy of Sciences. “Our test can identify an active infection relatively quickly and inexpensively. It also doesn’t depend on antibodies like many tests, but just identifies someone,” Ashwin Ramachandran explains. have been infected or not, not whether they are infected and therefore contagious, “said Ashwin Ramachandran, a Stanford Graduate and first author of the study.
Microlab testing takes advantage of the fact that coronaviruses like SARS-COV-2, the virus that causes COVID-19, leave microscopic genetic fingerprints wherever they pass as RNA strands. , a genetic precursor to DNA. If the coronavirus RNA is present in the cotton swab sample, the person sampled is infected.
To begin the test, the liquid from the cotton swab sample is dropped into the microlab, which uses the electric field to extract and purify any nucleic acid such as the RNA it may contain. The pure RNA is then converted into DNA and then replicated multiple times using a technique called isothermal amplification.
Next, the team used an enzyme called CRISPR-Cas12 – a brother of the CRISPR-Cas9 enzyme involved in this year’s Nobel Prize in Chemistry – to determine if any amplified DNA came from. coronavirus or not.
If so, the enzyme activated will activate the fluorescent probes to make the sample glow. Here, the electric field plays an important role by helping to gather all the important components – the target DNA, the CRISPR enzyme and the fluorescent probes – together into a space smaller than the fiber width. human hair, greatly increases their ability to interact.
“Our chip is unique in that it uses an electric field to clean nucleic acids from the sample and speed up a chemical reaction that tells us they’re present,” says Santiago.
The team created its device with a meager budget of around $ 5,000. Currently, the DNA amplification step has to be done outside the chip, but Santiago hopes that within a few months his lab will integrate all the steps into a single chip.
Some human-scale diagnostic tests use similar gene and enzyme amplification techniques, but they are slower and more expensive than the new test, giving results in as little as 30 minutes. Other tests may require more manual steps and can take several hours.
The researchers say their approach is not specific to COVID-19 and could be tailored to detect the presence of other harmful bacteria, such as E. coli in food or water samples. , or tuberculosis and other blood diseases.
“If we want to look for another disease, we just need to design the right nucleic acid sequence on the computer and email it to a commercial manufacturer of synthetic RNA. They send it back. Our molecule completely reconfigures our assay for a new disease, “Ramachandran said.
The researchers are working with Ford Motor Company to further integrate their steps and develop their prototype into a marketable product.
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Ashwin Ramachandran et al., Electric field-controlled microfluidics for rapid diagnosis based on CRISPR and its application to detect SARS-CoV-2, Proceedings of the National Academy of Sciences (Year 2020). DOI: 10.1073 / pnas.2010254117
Provided by Stanford University
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