The marvelous powers of mucus

While we may think of mucus as merely the slimy substance that clogs our nose and gets blown into a tissue, it's so much more. It lines several body organs, acting as a first line of defense against foreign invaders, as well as aiding essential body functions like digestion and illness prevention. And now scientists are taking inspiration from mucus for new disease-fighting treatments.

What is mucus made of?

Mucus is made of more than 95% water by weight, but its "key building blocks are mucins, which are long proteins decorated with complex sugars that make them look like bottlebrushes," said The New York Times. These mucins "attract and retain water, giving mucus its slippery, gel-like consistency," said New Scientist. This allows the mucus to keep the passages wet. "Once secreted, mucins crosslink with themselves and other compounds, creating a meshlike configuration," and the "more mucins in mucus, the denser this network becomes, resulting in smaller gaps or pores in its structure."

What can mucus do?

Mucus is a "masterpiece of biological engineering in my mind," said Katharina Ribbeck, a professor of biological engineering at the Massachusetts Institute of Technology, to the Times. It serves several purposes, from protecting us from pathogens to helping with digestion. "We are actually now learning more and more that it is very dynamic," said David Thornton, a biochemist at the University of Manchester, to New Scientist. "It is not just an inert barrier."

The goopy substance protects the human body in two ways by being both a physical barrier and a chemical barrier. It works by "shielding the body from unwanted objects and molecules," as well as "actively interacting with foreign materials," said New Scientist. "Mucus is almost like a bouncer at an exclusive nightclub, deciding who gets through." But that's not all it does. Mucus has an "important role in helping to smell, reproduce and have proper gut health, but it also plays an important role in how drugs are absorbed in the body," said Northeastern Global News.

It also "lines all our wet epithelial surfaces," Rebecca Carrier, a chemical engineering professor at Northeastern University, said to Northeastern Global News. This includes the nose, eyes, ears, throat, lungs, stomach and urological and genital tracts and more. Its composition and consistency on these different surfaces can vary as needed. For example, "human cervical mucus becomes thinner and more watery during ovulation, enabling sperm to penetrate it more easily," said New Scientist. "It might even respond to our body's internal clocks."

How can mucus help further medicine?

Researching how mucus works could open exciting possibilities in medicine. For example, mucins contain sugar molecules called glycans that can uniquely fight pathogens. Rather than killing them, the glycans are a food source for the bacteria. It's "like giving a kid a lollipop. They will calm down. Usually, they stop fighting," said Ribbeck to New Scientist. Treating the microbes this way "seems to tame them, rendering them less harmful." As a result, "one strategy could be to use glycans themselves, or molecules mimicking them, as alternatives to antibiotics or immunotherapies." This could also work without creating drug resistance, as can happen with antibiotics.