Mussel adhesion proteins have many applications, including medical and underwater construction, thanks to their strong adhesion and biocompatibility. With the development of mass production techniques, it is likely that this adhesive will become more widely used in our lives.
As evidenced by cosmetic advertisements that appeal to us with phrases like “don’t eat it, give it to your skin,” it’s not uncommon to see food ingredients performing multiple functions in our daily lives. This is not just limited to skin care; food ingredients now permeate our lives in a variety of ways. So, are there any food ingredients that fit the “don’t eat it, live it” mold? There is. It’s mussels.
I first saw mussels when I was a kid, fishing with my dad on the beach. Unlike the smooth stones of the land in front of our house, the stones on the beach were covered with tiny black stones. They could be found on rocks, in the bow of boats, and anywhere else the sea met the shore. At the time, it was just a curiosity, but over time, I began to think more deeply about their extraordinary abilities. I wondered how mussels could withstand such strong currents and stay firmly attached to rocks, and as I studied at university, I realized it was because of their ‘adhesive proteins’.
To stick to wet rocks, mussels secrete sticky threads on the rocks that adults call ‘adhesion proteins’. Rather than adhesion proteins, scientists explain that an amino acid called dihydroxyphenylalanine (DOPA) is the source of the adhesion. The mussels harden these sticky threads to form an adhesive pad about 2 millimeters in diameter, and each molecule that makes up the adhesive pad can be stuck on and off, much like the Scotch tape we all know and love. On average, a single mussel makes ten adhesive pads, each of which has been found to be capable of lifting about 12.5 kilograms of weight, meaning that a single mussel can lift about 125 kilograms of weight. The mussel’s adhesive proteins are of great interest because they can adhere to a variety of surfaces, including plastic, glass, metal, Teflon, and biomaterials.
This incredible adhesion means that mussels aren’t just sticking to rocks, but have the potential to be used in a wide range of applications. It’s too early to be alarmed. Mussel glue has medical applications because it doesn’t attack cells or trigger an immune response in living organisms. In fact, mussel adhesion proteins have already been used for medical purposes, with Professor Philip Messer Smith of Northwestern University in the US successfully saving the life of a fetus in a pregnant rabbit’s stomach with an adhesive made to mimic the adhesion protein. The pregnant mother rabbit had a congenital spinal deformity that required surgery, a risky procedure that involved cutting a hole in the fetal membrane surrounding the baby rabbit, which would have resulted in a premature birth. However, by applying mussel glue to the wound after the hole was cut, Smith was able to improve the 40% chance of survival to 60%, and the fetus survived.
The following experiment was conducted to determine the efficacy of mussel glue. Wounds on rats were sutured with regular surgical thread, chemically synthesized medical glue, and mussel glue, and the results were monitored. After two weeks, the sutured wounds were found to be open and not healing properly, with inflammation in the area. The wound healed without opening up, but there was a scar at the surgical site, and chemical adhesives have the disadvantage that they cannot be used on delicate skin. The only wound that healed without scarring was the one treated with mussel glue, which proved the effectiveness of mussel glue and made it popular in the medical community because of its harmless nature.
Mussel glue can be even more effective when operating on organs inside the body, such as the colon or bladder. The best way to operate on internal organs has always been to use surgical thread to create sutures, as medical chemical adhesives lose their adhesion due to the moisture in the body. But unlike conventional adhesives, mussel glue becomes stronger the wetter it gets, allowing patients to receive treatment with fewer side effects and a faster recovery.
But even the perfect glue, mussel glue, has a downside. It’s price. Commercially available mussel glue overseas costs about $75,000 per gram, as the protein must be manually extracted from more than 10,000 mussels to produce a single gram of mussel glue, which can lead to the ironic situation of killing more than 10,000 lives to save one, so mussel glue is rarely found in real life and is only used in research.
Recently, Korean researchers have developed a technology that can be mass-produced, which, if commercialized, could bring the cost of the expensive mussel glue down to a few hundred thousand won per gram. The aforementioned mussel adhesive protein can be used for a variety of purposes, from general household goods to high-value-added medical adhesives, drug delivery, and immobilization materials for cell cultures, and can be used in real life by replacing conventional chemical adhesives that can cause cancer. In addition, it is expected to become an indispensable material for underwater construction and ship building because it has the property of increasing adhesion when wet. It is expected that it won’t be long before the underwater city of Atlantis from the comics becomes a real-life metropolis. As such, mussel glue is likely to be at the center of future technology.
