According to the World Health Organization (who), in the three days from October 8 to October 10, the number of newly diagnosed patients with cowid-19 increased by 1 million. With the arrival of autumn and winter in the northern hemisphere, vicod is still facing severe control challenges. Rapid and accurate nucleic acid detection can help medical workers find patients infected with new coronavirus earlier, so as to treat / isolate them and track their contacts. < / P > < p > at present, most nucleic acid tests still need to send samples to special laboratories for processing, which often takes one day or even longer to obtain results, which may delay the time of treatment and isolation of patients. Therefore, researchers are working hard to develop a more rapid and simple nucleic acid detection method. Using CRISPR technology to accelerate the detection speed is one of the directions. Yao Ming Kant’s content team has previously reported the efforts of the team led by the famous scholar Dr. Zhang Feng and his collaborators to develop simple detection of new coronavirus using CRISPR technology. In order to make the detection more rapid and simple, Zhang Feng’s team’s stopcovid detection has gone through continuous iteration, not only using constant temperature PCR instead of traditional PCR, but also deleting the process of purifying RNA, and improving the detection sensitivity through optimization steps. < / P > < p > recently, a team led by Dr. Jennifer doudna, one of this year’s Nobel Prize winners in chemistry, and her partners published a paper on the preprint website medrxiv, which developed a new coronavirus detection method based on crispr-cas13a technology. The difference of this test is that it does not need to amplify the viral RNA by RT-PCR, and can directly detect the viral RNA level in the sample. The researchers also developed a detection system based on smart phone camera, so that medical staff can read the test results outside the laboratory environment without complex instruments. The core principle of < / P > < p > detection is not difficult to understand. The researchers used a combination of RNA and Caspar, an enzyme called CRISPR. When cRNA is combined with the specific sequence of viral RNA, cas13a can be activated. Cas13a is an interesting enzyme that, once activated, cleaves any other single stranded RNA molecules it encounters. Using this property, the researchers added a fluorescent molecule linked by RNA to the sample. Once cas13a is activated, the RNA on this particular molecule is cut off, releasing fluorescent molecules that emit fluorescence. In this way, by reading the fluorescence signal, we can detect the existence of virus specific sequence. < / P > < p > previous CRISPR detection based on this principle, in order to improve the detection sensitivity, the RNA in the sample should be amplified by PCR. However, this PCR step not only increases the detection time, but also means that the detection quantity will be limited by the supply of PCR reagents. < / P > < p > in this study, researchers used another method to improve the sensitivity of the detection. They speculated that since a CRNA binding to a virus specific sequence can activate the activity of cas13a enzyme, can two CRNAs binding to different virus specific sequences activate the activity of cas13a enzyme more quickly, making the rising speed of fluorescence signal faster? The < / P > < p > experiment also confirmed their hypothesis. When the researchers activated cas13a with two different crrnas, the growth rate of fluorescence signal increased significantly, although the total crrna level did not change. By measuring the growth rate of the fluorescence signal rather than the absolute value of the fluorescence signal, they found that the use of two CRNAs significantly improved the sensitivity of the detection. When one cRNA was used, the sensitivity of detection reached 10000 copies / microliter, while when two different CRNAs were used, the sensitivity increased to less than 1000 copies / microliter. < / P > < p > in order to further improve the detection sensitivity, researchers developed a CRNA detection method containing three different specific RNA sequences targeting new coronavirus. In the experiment of detecting five nasopharyngeal swab samples from patients with cowid-19, the detection accurately found these five positive samples, and the speed of fluorescence signal increase has a good correlation with the number of virus copies in the input samples The linear relationship further proved that this method can be used for quantitative measurement of virus level. < / P > < p > in order to prove that this simple detection can be used outside the laboratory, researchers built a simple fluorescence signal detection system based on the camera of smart phone. To their surprise, the sensitivity of the fluorescent signal detection system based on mobile camera is an order of magnitude higher than the commercial plate reader used in the laboratory. Using this simple fluorescent signal detection system, researchers can determine the positive nasopharyngeal swab samples of five patients with cowid-19 in only five minutes. < / P > < p > in the discussion, the researchers pointed out that smart phones are not only popular nowadays, but also have high camera sensitivity. More importantly, smartphones usually carry GPS and can be connected to the Internet. This makes it easier to transfer the read results to the cloud database to help contact tracking. The new coronavirus detection system based on smart phones may play an important role in controlling the current and future pandemic. Global Tech

By ibmwl