In this blog post, we will look at how the amazing adhesive proteins of mussels will change various fields, from medicine to underwater construction.
As you can see from cosmetic advertisements that appeal with phrases like “Don’t eat it, give it to your skin,” these days, we often see that food ingredients have multiple functions in our daily lives. This is not limited to skin care. Ingredients are now deeply ingrained in our lives in various ways. So, is there any ingredient that fits the “Don’t eat, give up on life” theme? There is. It’s mussels.
I first saw mussels when I was a child, when I went fishing with my father at the beach. Unlike the smooth stones on land that I used to see in front of my house, the stones at the beach were covered with small black pebbles. Young pebbles could be found anywhere where the sea meets the rocks, the bow of a ship, and so on. At the time, it just seemed strange, but as time went by, I began to think more deeply about the special abilities of mussels. I wondered how mussels could withstand such strong currents and stick so firmly to rocks, and as I studied my major in university, I learned that it was due to “adhesion proteins.”
To cling to wet rocks, mussels secrete a sticky thread on the rocks, which is called “adhesive protein” by adults. Scientists explain that the source of adhesion is an amino acid called “dihydroxyphenylalanine (DOPA)” rather than the term “adhesive protein.” The mussels harden this sticky thread to make an adhesive pad with a diameter of about 2 mm. Each molecule that makes up the adhesive pad can be repeatedly attached and detached like the scotch tape we commonly use. It has been found that a single mussel produces ten adhesive pads on average, each of which can lift about 12.5 kg. In other words, a single mussel can lift about 125 kg. The adhesive protein of mussels is attracting a lot of attention because it can adhere to various surfaces such as plastic, glass, metal, Teflon, and biomaterials.
Thanks to this amazing adhesive power, mussels not only stick to rocks, but also have the potential to be applied in various fields. It is still early to be surprised. Mussel glue does not attack cells or cause immune responses in organisms, so it can be used for medical purposes. In fact, there is a case in which the adhesive protein of mussels was used for medical purposes. Professor Philip Messer Smith of Northwestern University succeeded in saving the lives of fetuses in the bellies of pregnant rabbits with an adhesive made by mimicking the adhesive protein. The pregnant mother rabbit had a congenital spinal deformity and needed surgery, but the procedure involved puncturing the fetal membrane surrounding the baby rabbit, making it a risky operation with a high risk of premature birth. However, after making a hole in the fetal membrane and applying mussel glue to the wound, the chance of survival was increased from 40% to 60%, and the fetus was ultimately saved.
The following experiment was conducted to determine the efficacy of mussel glue. The wound of a rat was sutured with a general surgical thread, chemically synthesized medical glue, or mussel glue, and the progress was observed. Two weeks after the experiment, the suture area that was sutured with surgical thread was open and there was an area that did not heal properly, and inflammation occurred in that area. When the wound was sutured with a chemical synthetic adhesive, the wound area did not open and healed, but a scar remained on the surgical site, and the chemical adhesive had the disadvantage of not being able to be used on weak skin. The only case where the wound healed without a scar was the case treated with mussel glue, which proved the effectiveness of mussel glue through this experiment and received a call from the medical community because of the non-harmful nature of mussel glue.
Mussel glue can be more effective when operating organs such as the large intestine or bladder. When operating on internal organs, medical-grade chemical adhesives could not be used because of the moisture in the body, which reduced their adhesive strength, so the best method up until now was to use surgical sutures to perform suturing surgery. However, unlike conventional adhesives, mussel adhesive becomes stronger the more it is soaked, which allows patients to receive treatment with fewer side effects and faster recovery.
On the other hand, there is a downside to mussel glue, which is a perfect adhesive. It is the price. Commercially available mussel glue overseas costs about $75,000 per gram because it requires the manual extraction of protein from more than 10,000 mussels to produce 1 gram of mussel glue. Therefore, the irony of killing more than 10,000 lives to save one life may occur, so mussel glue is difficult to find in real life and is only used for research purposes.
Recently, a Korean research team has developed a technology that can mass produce mussel glue, and if this technology is commercialized, the unit price of expensive mussel glue can be reduced to hundreds of thousands of won per gram. The mussel adhesive protein mentioned above can be used for various purposes, from general household goods to high-value medical adhesives, drug delivery, and immobilization materials for cell culture. It can also be used in real life to replace existing chemical adhesives that can cause cancer. In addition, it has the property of increasing its adhesive strength when it gets wet, so it is expected to become a material that is essential for underwater construction and shipbuilding. It is expected that the underwater city of Atlantis, which we have seen in cartoons, will soon become a metropolitan city in the near future. Thus, mussel glue has a high potential to become the core of future technology.
