Covid-19: soon a rapid, portable and French test?

Portable, fast and reliable, the French Covidisc screening solution has passed an initial evaluation phase

Imagine a portable covid test, costing just $ 10, giving a result in less than an hour with a sensitivity equivalent to that of laboratory PCR techniques. This technology, capable of shaking up the world of diagnostics, is not a mirage. It already exists on French soil. Its effectiveness has recently been observed. And it is now subject to multiple checks before a possible production in large quantities, within a few months.

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Patrick Tabeling, research director at CNRS, professor at ESPCI-PSL, and responsible for this project called Covidisc, looks back on the discoveries that allowed his team to move forward. “It is a question of marrying two very precise technologies: that of LAMP amplification and” paper “microfluidics. The first was discovered in the early 2000s by a Japanese researcher. It improves the amplification phase. PCR techniques, a step used to make copies of the virus in order to better detect it in a sample. “Usually, during this phase, there are three temperature plateaus to reach. But the system, which rises to 95 degrees, must be precise. It does not tolerate large deviations from the prescribed values, which results in complex machinery. With the LAMP technique, the amplification temperature does not vary. It remains at 65 degrees which makes fitting much simpler “, explains Patrick Tabeling.

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Coupled with paper microfluidics, this isothermal amplification method allows a sample to be analyzed quickly, with less reagent, in equipment the size of a DVD. “Instead of using a centrifuge to extract the RNA from the virus, like in large testing labs, we use freeze-dried paper and biologics, like on pregnancy tests. When the surface of the paper gets wet, the Capillary forces pull the fluid to soak the entire surface. It’s the same thing when you put ink on a blotter: the task spreads spontaneously “, indicates the researcher. Despite the apparent simplicity of the process, Covidisc has required years of development in collaboration with the Institut Pasteur. And the main difficulty has only recently been resolved.

“The most complicated with microfluidics is to reproduce this phase of RNA extraction. Some companies try to get around the problem by diluting the sample several times inside a chip made up of micro-channels. . But their test then loses sensitivity. For the time being, paper microfluidics and its capillary forces give better results, “says Patrick Tabeling. The method also owes its effectiveness to the size of the samples analyzed. Contrary to popular belief, it has not been miniaturized in order to avoid collecting a viral load that is too low. Covidisc thus uses samples of 150 microliters (nasopharyngeal or salivary). A volume greater than that found in laboratory PCR machines!

When will it be launched on the market? “We are still in the verification phase”, insists the researcher. However, Covidisc already has a partnership with the company Bertin Technologies. It recently received funding of 400,000 euros from the city of Paris to produce the first series. If these see the light of day, the world of diagnostics could be permanently changed. “PCR was invented in 1983 and isothermal amplification in 2000”, recalls Patrick Tabeling. However, diagnostic giants like Roche, Abbott and Biomérieux still cling to their traditional testing methods, which are considered complex and expensive. With its paper, Covidisc could well force them to test new solutions.

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