What exactly is a flocked swab for nucleic acid test antigen detection?

As a new round of nucleic acid screening begins in Shanghai, a new rumor is spreading in the circle of friends.

The idea is that the nucleic acid test is not a swab, but a flocked swab, which contains carcinogens, and mysteriously says what flocked is you go check yourself.

1, flocking is a process, not a material

Flocking is not any plant lint, but a very common fabric treatment process, widely used in the textile industry, automotive manufacturing, printing, chemical industry and other fields.

Flocking process means that some short fibers that are cut or ground are fixed vertically to some kind of adhesive coated surface. The short fibers are usually nylon, polyester or other artificial fibers. The range of where they are flocked to is very wide, the surface of fabric, plastic, wood, leather, paper, etc. can be flocked.

Flocking only requires three things,

1. short fiber; 2. adhesive, 3. some kind of surface

Flocking is very common in everyone's life, just usually not realized. For example, flocked fabrics can be found on clothes, curtains, carpets, furniture, and usually those surfaces that are also comfortable to touch are brought about by the flocking process.

Flocking is also commonly used in car interiors, especially on the dashboard of rally cars, which are covered with flocked fibers to minimize the glare from the sunlight passing through the windshield.

In addition to the decorative role, flocking technology has also been tried to be applied by scientists in the production of graphene lithium battery negative sheet; making special oleophilic hydrophobic material to adsorb marine oil spills, etc.

2、The principle of flocking

At present, the most commonly used flocking method is electrostatic flocking. Let the flock enter the high-voltage electric field and contact the negative electrode with a negative charge, and be "sucked" by the electric field force on the side of the positive electrode, and accelerate almost vertically to the surface of the object to be flocked, and be firmly stuck by the glue applied to the surface of the object.

There are some fibers fall to the side not sticky, do not worry, they hit the positive electrode side, the surface of the negative charge is all neutralized, by the role of electrostatic electric field force will fall to the negative extreme, and then repeat the above movement, until they are stuck.

3、Flocking swab for nucleic acid detection

Nucleic acid detection with flocked swabs, "planted" on the material is mostly nylon staple fiber. Why to choose flocked nylon instead of cotton swabs, is for the functional needs of sampling.

Any material is designed for a purpose, and swabs for nucleic acid testing need to meet the following characteristics.

① have to be able to let the biological sample attached to it, can not scrape a little nothing picked a lonely.

② swab into the preservation solution after it has to "spill" the biological samples released, can not firmly hold the sample for a second can not be divided.

③ can not react with the biological sample, and destroy the sample.

As cotton itself has superior hydrophilicity and adsorption, creating once it is in contact with the sample, it is like the characters in the Joan of Arc play generally life and death.

In contrast, the nylon flocked swab is like a scum like "take it and leave it.

So nylon flocked swab than the traditional winding swab collection and release volume is much larger, experimental studies show that the flocked swab collection and release volume can reach 95% of the sample, while the cotton swab only about 20%.

This is because the fibers on the flocked swab are held vertically (OCD comfort) and the capillary action between the fibers encourages the sample to get "stuck" in the gaps. In fact, the swab is not bad at grabbing the sample, but after inserting the preserving solution, the flocked swab can quickly release the sample and let it elute, while the swab will let the cells get stuck in the fiber mass and cannot be separated.

In terms of sample preservation efficiency, the nylon flocked swab is more biocompatible and allows for more stable preservation of the sample. Otherwise the nucleic acid has been degraded before the test has begun that point, certainly can not measure the correct results.

Because of this, it is superfluous to worry that nylon is a synthetic fiber that is harmful to humans. Flocked fibers have even been tried in regenerative medicine to help repair injured bone and cartilage. By implanting a flocked fiber scaffold, the properties of the molded extracellular matrix allow stem cells to adhere to it to proliferate and differentiate; and provide enough space for the newly synthesized matrix and capillaries to enter.

Finally, human oral mucosa and nasal mucosa are not so fragile as to be destroyed by a scratch of this furry gadget. If you are not sure, please think carefully if there is another nylon thing rubbing around in everyone's mouth twice a day, all year round, and not hurting you (if you don't push too hard)