How to tell if your child is trying to forge Covid’s lateral flow test

Children are reportedly trying to forge a positive Covid cross-flow test with soft drinks.

But how are fruit juices, colas, and malicious kids cheating on the test and how to tell the fake positively? COVID Real result?

Mark Roach, a professor of science communication and chemistry at the University of Hull, reports that he has attempted an investigation. Wales online.. And this is what he is writing.

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First, I thought it was best to check the claims, so I broke an open bottle of cola and orange juice and then put a few drops directly into the LFT (immunography).

Sure enough, after a few minutes, each test shows two lines, which seems to indicate the presence of the virus that causes Covid-19.

It’s worth understanding how the test works. When you open the LFT device, you’ll find a strip of paper-like material called nitrocellulose and a small red pad hidden under a plastic case below the T-line.

Absorbed by the red pad are antibodies that bind to the Covid-19 virus. They are also attached to the gold nanoparticles (small gold particles actually look red), which allows you to see where the antibody is on the device. When performing the test, mix the sample with liquid buffer to ensure that the sample is kept at an optimum pH before dropping it onto the strip.

The liquid sucks up the nitrocellulose strip and picks up gold and antibodies. The latter also binds to viruses, if present. Further above the strip, next to the T (for testing), there are more antibodies that bind to the virus.

However, these antibodies cannot move freely – they are attached to nitrocellulose. As red smears of gold-labeled antibodies pass through this second set of antibodies, they also grab the virus. The virus then binds to both antibody sets and everything, including gold, remains immobilized on the line next to the T on the device, showing a positive test.

Gold antibodies that are not bound to the virus carry a strip that meets a third set of antibodies that are stuck on the C (control) line, which is not designed to pick up Covid-19. These trap the remaining gold particles without having to do so via the virus. This last line is used to indicate that the test worked.

Acid test

So how do soft drinks cause the appearance of red T-lines? One possibility is that the drink contains something that the antibody recognizes and binds to, similar to a virus. But this is quite unlikely.

The reason antibodies are used in such tests is that they are very noisy about what they bind to. There are all kinds of runny nose and saliva collected by cotton swabs taken from the nose and mouth, and antibodies completely ignore this protein confusion, other viruses, and the rest of the breakfast. Therefore, they do not react to the ingredients of soft drinks.

A more likely explanation is that something in the drink affects the function of the antibody. Various liquids have been used to fool tests, from fruit juices to cola, but all of them have one thing in common. It is very acidic. Citric acid in orange juice, phosphoric acid in cola, and malic acid in apple juice bring the pH of these beverages to 2.5-4. These are near-neutral pH conditions, which are quite harsh conditions for antibodies that have evolved to function primarily in the bloodstream. About 7.4.

Maintaining the ideal pH of the antibody is the key to the correct functioning of the test, which is the job of the liquid buffer that mixes the samples provided in the test. An important role of the buffer is due to the fact that when mixing cola and buffer (as shown in this rant of the Austrian politician’s claim that mass testing is worthless), the LFT works as expected. Emphasized: Negative for Covid-19.

Therefore, without buffer, the test antibody is completely exposed to the acidic pH of the beverage. And this has a dramatic impact on their structure and function. Antibodies are proteins, which are composed of amino acid components and bind to each other to form long linear chains. These chains fold into a very special structure. Even the slightest changes in chains can have a dramatic effect on protein function. These structures are maintained by a network of thousands of interactions between different parts of the protein. For example, the negatively charged portion of a protein is attracted to the positively charged region.

However, under acidic conditions, proteins become more and more positively charged. As a result, many of the interactions that hold proteins together are disrupted, affecting the delicate structure of proteins and causing them to malfunction. In this case, the antibody’s susceptibility to the virus is lost.

Given this, you might expect acidic beverages to be a completely blank test. However, denatured proteins are sticky beasts. Normally, all fully evolved interactions that hold proteins together are isolated and looking for binding. Therefore, it is possible that the antibody immobilized on the T-line attaches directly to the gold particles as it passes through, producing the infamous cola-induced false positive result.

So is there a way to find a fake positive test? Antibodies (like most proteins) can refold and regain function when they return to a more favorable state. Then, when the test in which cola was dropped was washed with a buffer solution, the antibody immobilized on the T line functioned normally, gold particles were released, and a true negative result was obtained. Buffers can be purchased online for a few pounds.

Kids, I applaud your ingenuity, but found a way to reveal your tricks, so use your cunning to devise a series of experiments and test my hypothesis. Is recommended. You can then publish your results to a peer-reviewed journal.

Mark Roach, Professor of Science Communication and Chemistry, University of Hull

This article will be republished from conversation Under a Creative Commons license. Please read the original article.

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