In this blog post, we explore the changes that the amazing adhesive proteins found in mussels could bring to various fields, from medicine to underwater construction.
As seen in cosmetic ads with slogans like “Don’t eat it—use it on your skin,” we frequently see food ingredients serving various functions in our daily lives these days. This isn’t limited to just skincare. Food ingredients are now deeply integrated into our lives in diverse ways. So, is there a food ingredient that fits the phrase “Don’t eat it—use it in your daily life”? There is. It’s the mussel.
I first saw mussels when I went fishing at the beach with my father as a child. Unlike the smooth, touchable rocks I saw near my house, the rocks by the sea were covered with tiny black pebbles clinging tightly to them. These tiny shells could be found anywhere the sea met land—on rocks, ship bows, and so on. At the time, they just seemed fascinating, but as time went on, I began to think more deeply about the special ability mussels possess. I wondered how mussels could withstand such strong currents and cling so firmly to rocks, and when I entered university and studied my major, I learned that it was due to “adhesive proteins.”
To attach themselves to wet rocks, mussels secrete a sticky thread—what adults call “adhesive protein”—onto the surface. Scientists explain that the source of this adhesive strength is not the term “adhesive protein” itself, but rather an amino acid called “dihydroxyphenylalanine (DOPA).” Mussels harden these sticky threads to form adhesive pads about 2 mm in diameter, and each molecule in these pads can repeatedly stick and unstick, much like the Scotch tape we commonly use. It has been found that a single mussel creates an average of ten adhesive pads, and each pad can lift a weight of about 12.5 kg. In other words, a single mussel can lift a weight of about 125 kg. Mussel adhesive proteins are attracting significant attention because they can adhere to a wide variety of surfaces, including plastic, glass, metal, Teflon, and biological materials.
Thanks to this remarkable adhesive strength, mussels are not merely limited to clinging to rocks but hold the potential for applications in various fields. But don’t be surprised just yet. Mussel adhesive does not attack cells or trigger an immune response within living organisms, making it suitable for medical use. In fact, there have been cases where mussel adhesive proteins have been used in medicine. Professor Philip Messer-Smith of Northwestern University successfully saved the life of a fetus inside a pregnant rabbit using an adhesive modeled after the mussel’s adhesive protein. The pregnant mother rabbit had a congenital spinal deformity that required surgery. However, the procedure involved puncturing the amniotic sac surrounding the fetus, making it a high-risk operation with a high probability of premature birth. However, by applying mussel adhesive to the wound site after puncturing the amniotic sac, the survival rate was increased from 40% to 60%, and as a result, the fetus survived.
To investigate the efficacy of mussel adhesive, the following experiment was conducted. In this experiment, wounds on mice were sutured using standard surgical sutures, chemically synthesized medical adhesives, and mussel adhesive, and the outcomes were monitored. The results showed that two weeks later, the sutured areas treated with surgical thread had opened up in some places, failing to heal properly, and inflammation developed in those areas. In cases where the wounds were closed with chemically synthesized adhesive, the wounds healed without opening, but scars remained at the surgical sites; furthermore, chemically synthesized adhesives had the disadvantage of being unsuitable for use on delicate skin. The only cases that healed cleanly without scarring were those treated with mussel adhesive. This experiment proved the effectiveness of mussel adhesive, and due to its non-toxic nature, it began to attract significant interest from the medical community.
Mussel adhesive can be even more effective when used in surgeries on internal organs such as the large intestine or bladder. Until now, the best method for internal organ surgery was suturing with surgical thread, as conventional chemical adhesives lost their adhesive strength due to the body’s moisture and could not be used during such procedures. However, unlike traditional adhesives, mussel adhesive becomes stronger the wetter it gets, allowing patients to receive treatment with fewer side effects and faster recovery times.
On the other hand, even this perfect adhesive has a drawback: its cost. Commercially available mussel adhesive overseas costs approximately $75,000 per gram, as producing just 1 gram requires manually extracting protein from over 10,000 mussels. Consequently, the ironic situation where over 10,000 lives are taken to save a single life could arise, making mussel adhesive difficult to find in everyday life and limiting its use to research purposes.
Recently, a Korean research team developed a technology capable of mass production, and if commercialized, this technology could reduce the unit price of the expensive mussel adhesive to several hundred thousand won per gram. The mussel adhesive protein mentioned earlier can be utilized for a wide range of applications, from general household goods to high-value-added medical adhesives, drug delivery systems, and immobilization agents for cell culture. Furthermore, it can replace existing chemical adhesives that may cause cancer, making it suitable for everyday use. Additionally, since its adhesive strength increases when wet, it is expected to become an essential material for underwater construction and shipbuilding. It is predicted that it won’t be long before the underwater city of Atlantis, once seen only in comics, becomes a real-life metropolis. As such, mussel adhesive has a high probability of establishing itself as a core component of future technology.
