frog secretions for surgery?

Par Shabnam Zaman – PhD Researcher in Biology, Vrije Universiteit Brussel

New research has uncovered how some frogs produce glue that could help us make innovative new adhesives for surgery.

You probably know the story of The Frog Prince, in which a princess kisses a frog who, to her great surprise, turns into a prince.

In fact, many species of frogs produce a poison in their skin, the effects of which can range from mild nausea to death, so this display of affection is generally discouraged. But what if the frog had found a more unusual way to defend itself, leaving our heroine’s lips sealed with the kiss ?

Biological adhesives: a story as old as time

While man mainly uses materials synthetic materials for gluing objects together, our princely frog – like other glue-producing organisms – produces what is called a “biological adhesive”. These naturally secreted substances are widespread among animals and are often essential for their survival.

For example, mussels produce a type of glue that permanently attaches them to underwater surfaces, while other animals living in the ocean, such as starfish, use another, much more temporary type of glue. , to help them move around.

On land, the most famous example is spider glue, which it uses to create silk to capture prey. If we focus on the vertebrates terrestrial, the stickiest specimens are the feet of geckos and those of certain tree frogs. These are examples ofmembership “dry” and “wet”, meaning that geckos stick to surfaces without producing anything resembling glue, while tree frogs’ pads are covered in a thin layer of slime or mucus.

Despite their obvious differences, these two types of adhesion have been described as “self-cleaning” and could help us develop synthetic materials that share this characteristic. Indeed, the way different biological glues are formulated and then secreted often involves wondrous feats of natural engineering.

In other cases, however, glue secretion has little to do with complex geometric operations, but rather with shedding large quantities of slime all at once.

Sticky secretions: an unlikely defense mechanism

Of the traditional medicine to shamanic rituals, tales and myths, frogs and toads are of great cultural importance throughout the world. Frogs’ poison glands are particularly important, as they can be used to make weapons, cures, or even hallucinogens.

Until now, studies of defenses secreted by amphibian skin have focused on molecules that function as toxins. However, in addition to being purveyors of poison, a small number of species (including the world’s largest amphibian, the Chinese giant salamander) have evolved a strategy most original survival tool: glue.

When stressed, the animal’s skin releases a thick fluid that becomes extremely sticky within seconds. From the frog’s perspective, this stress usually takes the form of an attack by a predator (or princess). The speed at which the slimy secretion – sticky slime, in reality – turns to glue makes it almost impossible for a predator to ingest the frog, probably due to the discomfort of having its mouth and face coated of glue.

Although this tactic may seem crude and inelegant, it is an effective defense mechanism because it gives the frog time to escape.

Trace the evolutionary mechanisms

Although glue is a rare feature in frogs, it has evolved several times in species spread across different continents. My recently published research explores the origins of this remarkable survival strategy and explains why it is present in some frogs and not others.

To answer these questions, we first had to identify the ingredients responsible for the stickiness of frog glue. To do this, we used technologies ranging from low-tech Lego bricks to high-tech microscopes capable of magnifying to the nanoscale (a billionth of a meter).

Surprisingly, the basic ingredients needed to make this glue exist in almost all animals, including humans, but only amphibians have developed the set of tools necessary to transform them into glue. And even among amphibians, only a few species, which live at distances as far apart as Madagascar, Brazil and Australia, have evolved this ability.

We discovered that the Mozambique rain frog, which is separated from the tomato frog by about 100 million years of evolution, uses the same basic ingredients and toolbox to create its own adhesive secretion.

From biology to biomimicry: a very sticky surgical solution

Frog glue is fascinating, it’s fast and flexible, meaning it has huge potential for practical applications. That’s where biomimetics comes in, a field that strives to mimic biological processes that took nature millions of years to develop.

Thanks to our research, we now know, for the first time, how a four-legged animal produces glue. Imagine that medical adhesives inspired by frog glue could be used as surgical glues: not only is it strong and non-toxic, but it is able to adapt and adhere to virtually any surface.