This bodily fluid is not that disgusting

Whether it's snot, phlegm from the lungs or secretions from a bleeding wound: many people think “yuck!” when they see mucus. But this often underestimated body fluid plays a vital role in our health.

It’s the first line of defense against pathogens, home to our microbiome, and the conveyor belt of our digestion that keeps everything running smoothly.

Even in ancient times, mucus was given a central role: as one of the four body fluids, along with blood, black bile and yellow bile, they were supposed to maintain balance with health and well-being. Today, thick discharge is more likely to be considered a disgusting carrier of disease.

Mucus – or mucus – is more than just a phlegm product of the body: as a natural lubricant, it is important for swallowing and digestion, for example, preventing the penetration of pathogens in the form of nasal secretions or cervical mucus, protecting the stomach wall from gastric acid, and houses much of the human microbiome, such as gut flora.

Produces more than a liter of mucus per day

Overall, the human body produces an average of about one and a half liters of mucus per day. The composition of this gel-like substance, which is mostly made up of water, proteins, antibodies and enzymes, varies depending on the part of the body. Certain glycoproteins, so-called mucins, are responsible for the structure of mucus. By interacting with their respective environments, they determined whether the mucus was thin (as in the lungs) or thick (as in the stomach).

These mucins may play an important role in neutralizing dangerous bacteria that try to enter the body through the nose. Contrary to previous thinking, mucus may not act as a barrier; instead, sugar molecules in mucin can disrupt bacterial signaling, rendering them harmless. At least, that's according to a 2019 study published in Nature Microbiology by German biophysicist Katharina Ribbeck, who studies mucus at MIT.

The study notes that it's not yet possible to answer exactly how mucin tames bacteria. However, if the corresponding bioactive sugar molecules are identified, this could help develop “a class of therapies to treat persistent bacterial infections.”

Bioink made from mucus

That's not the only conceivable application: In a study published in June in the journal ACS Applied Bio Materials, an Indian research team proposed a mucin-based bioink for 3D printing of lung tissue. One day, this ink could be used to create 3D lung models to study lung diseases and test possible treatments.

At the Technical University of Munich, under the supervision of Oliver Lieleg, research is also being conducted on the medical applications of mucin, including bioinks made from mucin. Lieleg, who has been working on the subject for 15 years, attributes the great potential of complex slime molecules to their different properties: they can bind large amounts of water, stick to many surfaces, but inhibit the stickiness of other objects very well. Attached. “But the opposite is also true: for example, viruses bind very well to mucin, which is part of the mucus' job so that we don't end up in bed with colds all the time.”

contact lens lubricant

Furthermore, mucin is well tolerated as the body's own material, an important property for possible medical uses, including special coatings for contact lenses or cannulas. To do this, Lilleg's team took advantage of the fact that mucin is a good lubricant: “Contact lenses and cannulae are hard materials that, in the worst case, can cause damage to soft tissue.” Based on mucin The protein coating minimizes this irritation – and, in the case of contact lenses, ensures that lipids from the eye’s tear film don’t deposit on the lens.

Mucin has important medical uses, including special coatings for contact lenses.Image source: Associated Press

Lieleg's research team takes mucus molecules from pig stomach mucus, dilutes them and chemically cleans them until the end result is pure mucin with the consistency of marshmallows.

In addition, researchers have developed a wound-healing patch specifically for soft tissue injuries such as the tongue or intestines. The prototype contains a mucin component that has an antibacterial effect and thus prevents the wound from being contaminated.

Lileg and his team are also studying possible disorders of the mucus system and have shown that fine dust particles can affect the mucus barrier. The team is currently conducting similar research on microplastic particles. “Mucus absorbs many substances from the external environment that come into contact with our mucous membranes,” Lilleger concluded. “If contaminants weaken this barrier, things may get through, but they shouldn't.”

Unjustifiable bad image

“I think we just underestimate how important mucus is to us,” the scientist stressed. Without mucin in the tear film, blinking becomes difficult over time. Certain clinical signs manifest as reduced mucin production, such as in saliva. “Without proper lubrication, speaking and swallowing can be painful,” Lilleg said.

The reason we don't get sick all the time is thanks to mucus molecules, which absorb a lot of stuff: “What comes out of your nose may not look good, but that's because of tiny dust particles or large chunks of mucus molecules. “Fortunately, the flu virus came from my office neighbor. “Slime has such a bad image. “I think a lot of people don't know how important it is to our daily well-being. ” (Sudan Development Authority/Department of Political Affairs)

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