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    Home > Medical News > Medical World News > The team of the winners of the New Jinno Prize developed a simple new coronavirus detection without PCR can be quantified on mobile phones.

    The team of the winners of the New Jinno Prize developed a simple new coronavirus detection without PCR can be quantified on mobile phones.

    • Last Update: 2020-10-23
    • Source: Internet
    • Author: User
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    According to the World Health Organization (WHO), the number of newly diagnosed COVID-19 patients worldwide increased by 1 million in the three days from October 8 to October 10.
    with the arrival of autumn and winter in the northern hemisphere, control of the COVID-19 epidemic still faces serious challenges.
    and accurate nucleic acid testing can help health care workers detect patients infected with the new coronavirus earlier, allowing them to be treated/isolated and contacted.
    Most nucleic acid tests today still require samples to be sent to specialized laboratories for processing, often for a day or more to obtain results, which can delay the treatment and isolation of patients.
    , researchers are working together to develop faster and easier nucleic acid detection.
    one of the directions is to use CRISPR technology to speed up detection.
    's content team has also previously reported on the efforts of a team led by renowned scholar Dr. Zhang Feng and his collaborators to develop simple new coronavirus detection using CRISPR technology.
    In order to make detection faster and easier, Zhang Feng's STOPCovid detection has been iterative, not only using thermostat PCR instead of traditional PCR, but also reducing the process of purifying RNA, and improving the sensitivity of the detection through optimization steps.
    , a team led by Dr. Jennifer Doudna, one of this year's Nobel Laureates in Chemistry, and her partners published a paper on the preprinted site medRxiv, developing a new type of coronavirus detection based on CRISPR-Cas13a technology.
    this test is unique in that it does not require the use of RT-PCR amplification of viral RNA, which directly quantifys the level of viral RNA in the sample.
    researchers have also developed a smartphone-based camera detection system that allows medical staff to read test results in environments outside the lab without the need for sophisticated instruments.
    the core principle of improving the sensitivity of CRISPR detection without PCR is not difficult to understand.
    researchers used an enzyme called Cas13a and a combination of CRISPR RNA (crRNA) to form a complex.
    when crRNA is combined with specific sequences on viral RNA, Cas13a enzymes can be activated.
    Cas13a is an interesting enzyme that, once activated, indiscriminately cut through any other single-stranded RNA molecules encountered around it.
    this property, the researchers added a fluorescent molecule connected by RNA to the sample.
    Cas13a is activated, the RNA on this particular molecule is cut off, releasing fluorescent molecules that emit fluorescence.
    this way, the presence of virus-specific sequences can be detected by reading fluorescent signals.
    CRISPR detection, which was previously based on this principle, amplifies the RNA in the sample via PCR in order to increase the sensitivity of the test.
    this PCR step not only increases the time required for testing, but also means that the number of tests is limited by the supply of PCR reagents.
    researchers used another method to improve detection sensitivity using crRNA using multiple virus sequences that target different virus sequences (Photo: Source: Resources.
    They speculated that since a crRNA binding to a virus-specific sequence activates the activity of Cas13a enzyme, will two crRNAs binding to different virus-specific sequences activate the activity of Cas13a enzyme more quickly, making fluorescent signals rise faster? The experiment also confirmed their hypothesis.
    when the researchers activated Cas13a enzymes using two different crRNAs, although the overall crRNA levels did not change, the growth rate of fluorescent signals increased significantly.
    by detecting the growth rate of the fluorescent signal rather than the absolute value of the fluorescent signal, they found that using two crRNAs significantly improved the sensitivity of the detection.
    When using one crRNA, the sensitivity detected reaches 10,000 virus copies/microliters, while when two different crRNAs are used, the sensitivity is increased to less than 1000 copies/microliters.
    To further improve the sensitivity of the test, the researchers developed crRNA with three specific RNA sequences targeting the new coronavirus, which was accurately found in an experiment that tested five nasopharyngeal swabs in five COVID-19 patients, and the increase in fluorescent signals was well linear with the number of virus copies in the input sample, further demonstrating that the test could be used to quantify virus levels.
    using a smartphone's camera to build an easy signal reading system to prove that this simple detection can be used in environments outside the lab, the researchers built a simple fluorescent signal detection system based on the smartphone's camera.
    surprised them, the fluorescent signal detection system based on mobile phone cameras was an order of magnitude more sensitive than the commercial plate reader used in the lab.
    using this simple fluorescent signal detection system, the researchers were able to determine that five patients with COVID-19 had a positive nasopharyngeal swab sample in just five minutes.
    a fluorescent signal reading system based on smartphone cameras (Photo Source: Resources) researchers note in the discussion that smartphones are not only popular today, but also have high camera sensitivity.
    more important is that smartphones usually carry GPS and can be connected to the Internet.
    this makes it easier to transfer read results to a cloud database and assist contact tracking.
    new smartphone-based coronavirus detection system could play an important role in controlling current and future pandemics.
    resources: s1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Retrieved October 12, 2020, from Fozouni et al., Direct detection of SARS-CoV-2 using CRISPR-Cas13a and a mobile phone. medRxiv, doi: follow medicinalcond.
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