Professor Zhang Feng’s team has developed a method to detect new coronavirus RNA using CRISPR-based technology, the McGovern Institute for Brain Sciences at the Massachusetts Institute of Technology (MIT) announced today. It requires only a purified sample of nucleic acid molecules, which can be tested in just three steps in an hour.
Because the technique is still relatively preliminary and has not been tested in real patient samples, scientists also stress that the method is not currently available for clinical diagnosis of neo-coronavirus infection.
Sherlock Holmes with the golden eye of fire
In the related paper, Professor Zhang Feng’s team pointed out that in the face of the outbreak of new coronavirus, the main detection method is qPCR. But we also need to be aware that the reagents and equipment required for qPCR are not always readily available. To some extent, this also affects the speed at which the disease is diagnosed. To advance the diagnosis of disease, researchers are also developing new diagnostic tools. The tools they describe in their papers were born on this premise.
THE TOOL USES THE SHERLOCK TECHNOLOGY PUBLISHED BY PROFESSOR ZHANG FENG’S TEAM IN THE 2017 ISSUE OF SCIENCE. This technique, which has the same name as Sherlock Holmes, is an acronym for “Specific High Sense Select Y Select Image Reporter UnLOCKing” technology. In terms of name, it has a unique high sensitivity.
The study is based on a study in the 2017 issue of the journal Science (Photo: Supplied)
And based on the birth of CRISPR technology, it does have a Sherlock Holmes-like “fire eye gold eye.” In a 2017 paper in Science, researchers point out that the system is sensitive to both RNA and DNA at the single-molecule level.
Technical principles for detecting new coronaviruses
In principle, this technique is not difficult to understand. AT THE HEART OF SHERLOCK IS AN ENZYME CALLED CAS13A AND A GUIDE RNA THAT BINDS TO IT. Based on the RNA sequence of the new coronavirus, the researchers designed two wizard RNAs, one to identify the S gene for the new coronavirus and the other to identify the Orf1ab gene. To maximize the accuracy of detection, scientists selected the most new coronavirus-specific sequences. In this way, interference from other respiratory virus genomes can be minimized.
Based on this design, the wizard RNA could, theoretically, accurately identify the RNA corresponding to the new coronavirus, and activate the Cas13a protein that binds to it. Cas13a is an interesting enzyme that, once activated, frantically cuts open any other RNA molecule it encounters. It is also with this characteristic that the researchers added a special molecule to the sample that is connected by RNA. Once Cas13a is activated, rna on this particular molecule is cut off. In this way, by confirming that these molecules have not been cut off, we can know if there is a new coronavirus in the initial sample.
By confirming that these molecules have not been cut off, we can know if there is a new coronavirus in the initial sample (Photo: Resources 3)
In general, subsequent testing does not require too many tedious steps, and all that is needed is a test paper that specifically identifies “complete molecules” and “cut-off molecules”. If there is no new coronavirus in the sample, then a band appears at the lower position of the test paper labeling the “complete molecule”, and if there is indeed RNA corresponding to the new coronavirus in the sample, another band appears at the higher position representing the “cut-off molecule”. With different stripe locations, it’s easy to confirm the presence or absence of a new coronavirus.
By different locations of the stripe, we can determine if there is a new coronavirus (Image Source: Resources 1)
Three easy steps in just 1 hour
Professor Zhang Feng’s team also described the steps to carry out this test. The full process can be clicked on “Read the original/Read More” at the end of the article, with only a few key information listed here:
The extracted nucleic acid samples were amplified by conventional same-temperature amplification techniques. This step takes 25 minutes and lasts 42 degrees Celsius.
Add Cas13 protein, wizard RNA, and special molecules that report to the sample. Then at 37 degrees Celsius, continue to react for 30 minutes.
Use the test paper to test the samples obtained in the second step. This step takes about 2 minutes to react.
In tests, the researchers said, they were able to consistently detect the sequence of the new coronavirus, and were highly sensitive — only 100 copies, or even 10 copies, could be detected per microliter.
Overall, the researchers note that simply isolating RNA from a patient’s body and using these steps can be diagnosed within an hour without the need for complex devices. Anyone interested in testing the technology can apply online for the material (https://www.addgene.org/91909/or firstname.lastname@example.org).
But they have also repeatedly stressed that the technique has not yet been used in patient samples and is therefore not validated and cannot be used directly for clinical diagnosis. They will also work with other researchers to keep up-to-date with the latest technical guidance online.
It is worth noting that the World Health Organization made it clear at this week’s research conference on new coronaviruses that “the development of accurate and easy-to-use diagnostic tests” is a top priority. We also look forward to the early validation of this technology to assist patients in their diagnosis.