The bear kid’s new method of skipping classes: use juice cola to get a false new crown positive result
For this, foreign media reporters started to research. It is reported that the reporter opened the Coke bottle and orange juice, and then dropped them directly on the LFT. Sure enough, after a few minutes, two lines appeared in each test, which is said to indicate the presence of a virus that can cause COVID-19.
It is worthwhile to understand how these tests work. If you open an LFT device, you will find a strip of paper-like material-called nitrocellulose-and a small red pad-hidden under the plastic casing under the T-line. It is reported that the red pad absorbs antibodies that bind to the COVID-19 virus. In addition, they are attached to gold nanoparticles (tiny gold particles are actually red) so they can see where the antibodies are on the device. When doing the test, the tester mixes his sample with a liquid buffer solution to ensure that the sample is maintained at an optimal pH value, and then drops it on the test paper.
The liquid will absorb the nitrocellulose sliver And take away the gold and antibodies. If the virus exists, the latter will also combine with the virus. Further up, the part near the T (for testing) has more antibodies bound to the virus. But these antibodies cannot move freely-they are glued to nitrocellulose. When the red and gold-labeled antibodies pass through the second set of antibodies, these antibodies will also catch the virus. Then, the virus will combine with the two sets of antibodies-fixing everything including gold on the line next to the T on the device, which means that the test result is positive.
The gold nanoantibodies that are not bound to the virus will continue to encounter the third group of antibodies on this line. This group of antibodies is not designed for COVID-19 infection and is stuck on the C (control) line . They can capture the remaining gold nanoparticles without passing through the virus. The last line is used to indicate that the test has been completed.
So, how did soft drinks cause the appearance of the red T-line? One possibility is that these drinks contain things that antibodies recognize and bind, just as antibodies recognize viruses. But this is quite impossible. The reason antibodies are used in this type of test is that they are very picky about the object they bind to. The cotton swabs that people extract from the nose and mouth collect various substances in snot and saliva, but antibodies completely ignore these proteins, other viruses, or breakfast residues, so they will not react to the ingredients in soft drinks.
A more likely explanation is that something in the drink affects the function of the antibody. From juice to cola, many liquids are used to fool the test, but they all have one thing in common-they are all highly acidic. The citric acid in orange juice, the phosphoric acid in cola, and the malic acid in apple juice make the pH of these beverages between 2.5 and 4. This is a very harsh condition for antibodies. It is reported that the ideal test pH for this test is almost neutral, about 7.4.
Maintaining the ideal pH value of the antibody is the key to testing the correct function, which is exactly what the liquid buffer solution of the mixed sample has to do. The key role of the buffer is that if you mix Coke and the buffer together, then LFT will behave as you would expect: negative for COVID-19.
So if there is no buffer, the antibody under test will be completely exposed to the acidic beverage. This has a huge impact on their structure and function. Antibodies are proteins, composed of amino acids, joined together to form long, linear chains. These chains will fold into a very special structure. Even small changes in the chain can significantly affect the function of a protein. These structures are maintained by a network of thousands of interactions between different parts of the protein.
But under acidic conditions, proteins will become more and more positively charged. As a result, many of the interactions that hold the protein together are disrupted, the delicate structure of the protein is affected, and it no longer works properly. In this case, the antibody loses sensitivity to the virus.
All those perfectly evolved interactions that normally hold proteins together are now orphans, and they are looking for something to combine. Therefore, one possible explanation is that the antibody immobilized at the T line directly adheres to the gold nanoparticles when they pass by and produces a cola-induced false positive result.
So is there a way to detect false positive tests? Antibodies, like most proteins, can refold and restore their function when they return to more favorable conditions. So when I tried to wash a test with a buffer dipped in Coke, the antibody immobilized at the T line resumed its normal function, which released gold particles and revealed the true negative result of the test.