Current Covid 19 diagnostic tests are mainly performed using the annoying nasal swab sampling method, and the time to determine the result is long. Accurate diagnostic test is PCR test, which is considered to be the gold standard of Covid 19 diagnosis; But the waiting time is also long; For this reason, we cannot rely on it to control the virus while we are waiting for the vaccine; Because it has a slow process.
Antigen tests are fast; Like the case with the Food and Drug Administration this week for home use approved. However, they do have problems with test sensitivity; Therefore, health officials continue to emphasize the need for rapid and reliable testing.
Recently, a new wave of rapid molecular tests with PCR test sensitivity and antigen test speeds have been validated and are moving from the prototype to FDA approval. In the last two weeks, studies published in journals Science Advances And Cell They detail these Covid 19 hypersensitive molecular experiments based on Crisper gene editing technology.
These plausible tests are powered by smartphones and deliver results in about 15 to 30 minutes. Melanie August, One of the authors of the study published in Cell Magazine, says:
Crisper is still a relatively new method on the market and it is interesting that it is part of the first wave of Crisper diagnostic tools. Combining it with mobile phones helps us bring the diagnosis closer to people, so that everyone can use it.
Crisper is coming
March, Tony Ho, A biomedical engineer from the University of Toulon, USA, wondered if saliva could replace nasal swabs as a tool for detecting Covid 19. Recent studies confirmed his speculation about the presence of the virus in saliva; But the concentration of the virus in saliva is low. Hu noted that detecting the virus in saliva requires very sensitive technology; Therefore, they turned to Crisper, which had previously been used to diagnose Zika virus.
Unlike PCR, Crisper technology can detect and label viral proteins without the need for RNA cleavage. If RNA separation is like navigating a haystack looking for needles, crisper is like using a magnet to catch them.
The tulin test, described in the Science Advances article, combines a saliva sample with a solution of chemicals to amplify a small region of viral RNA about 100 million times. In the next step, the guide RNA, called Cas12a, finds the RNA sequence of the Corona virus M protein and attaches to it. When the Cas12a guide binds to M protein RNA, the crisper complex cleaves a fragment of Cas12a and the DNA probe attached to it, and the probe glows due to its fluorescence property.
Hu says the mobile phone camera is sensitive enough to detect glare from Cas12a guides. Bo Ning“While it seems complicated, everything is done in two quick steps using a microfluidic chip, and it’s easy for everyone to do,” says the assistant professor at the University of Toulon and lead author of the paper.
Smartphone-based Covid 19 experiment uses Crisper to detect corona virus RNA in saliva sample, determines result in 15 minutes
The test showed results from a saliva sample in 15 minutes and, as expected, detected lower concentrations of the virus than conventional PCR tests. The experiment was very specific; Because when the researchers tried to deceive it with more than thirty other respiratory pathogens, it did not cross-react and did not produce false positive results.
This method is licensed to NanoPin Technologies. Nanopin is a diagnostic company founded in 2017 and Hu is one of its founders and scientific advisor. According to the company’s CEO, Nanopin plans to submit a laboratory kit version of the saliva test to receive an emergency use permit from the FDA by the end of January. Then, in the next six months, move on to making smartphone-based versions.
Detection without duplication
Two years ago, a team of scientists from the Goldstone Institute and the University of California began building a home test for HIV that, like the Corona virus, contains the genetic material RNA. When the birth of Covid 19 began, researchers led Melanie August And Daniel Fletcher, From the University of California at Berkeley and Jennifer DudnaCrisper discovers technology to detect Covid 19 virus, SARS-CoV-2. “All we needed to adapt the method for the new virus was the virus genome sequence, which became available in January,” August said.
Scientists at the University of California have done just that. Their method uses three Cas13 guides to hunt for fragments of virus RNA in nasal swab samples. During the experiment, the method detected small amounts of the virus, which reached 100 copies per microliter of the sample, in less than 30 minutes, and detected higher concentrations, such as those found in highly contagious individuals, in less than 5 to 5 minutes.
The California test is unique in that it does not require viral RNA to be amplified first (as required by PCR tests, Lucira Health home tests, and tulen group tests). By eliminating the amplification step, August says, the results are a direct measure of the amount of RNA in the sample. This information can help doctors chart the course of a person’s illness and better find appropriate treatments.
The experiment, led by researchers at the Goldstone Institute, detects the corona virus in the nasal swab using three small Crisper guides to bind to viral RNA, and in the presence of viral sequences, produces a fluorescent glow that a smartphone can detect.
The team is now testing a prototype home test that will eventually cost less than $ 10 per cartridge. August says they expect to move to FDA approval in a few months.
Can a quick test save us?
Some researchers, in particular Michael MinaHarvard University calls for rapid and frequent testing using antigen tests to monitor and control the virus. Antigen testing is less sensitive, and others argue that the strategy suffers from problems such as limited access to the test and the effect of uncertain test accuracy. New Crisper-based experiments, such as those described above and other molecular experiments that are under construction, can address these concerns and enable repeated and accurate testing throughout society if approved.
Hu and August imagine their experiments being used in schools, airports, offices, and many other places. For example, a travel company contacted Hu about using the technology. The ultimate goal for both is to make home test kits; But many standards are needed to validate these, especially for newer technologies such as Crisper.