Barnacles’ ability to cling to wet, slimy surfaces causes headaches for the maritime industry, but it could be a boon to medicine. Inspired by barnacle glue, a team of researchers from MIT and clinicians from Mayo Clinic have developed a medical paste made of adhesive proteins embedded in a hydrophobic matrix that can seal bleeding, injured tissue in seconds (Nat. Biomed. Eng. 2021, DOI: 10.1038/s41551-021-00769-y).
In traumatic injury cases, blood loss is the leading cause of death among the military and second among civilians. Stitching up a gushing wound takes time that emergency situations often don’t have. While topical hemorrhage treatments are available, they work by accelerating natural blood clotting, which can take several minutes and doesn’t always work on heavily bleeding wounds or for patients whose blood can’t clot.
In 2019, Hyunwoo Yuk and colleagues of the Massachusetts Institute of Technology developed an adhesive capable of adhering to wet tissue. Made of the biopolymer chitosan, poly(acrylic acid), and N-hydroxysuccinimide ester, the tape sticks by covalently cross-linking with amine groups on the tissue’s surface.
The team showed that the tape could close surgical incisions on wet tissue. But in profusely bleeding wounds, the steady flow of liquid makes it challenging for an adhesive to reach the surface and seal the opening. Yuk looked to barnacles, which have evolved to thrive in a similarly wet and turbulent environment. When a barnacle attaches to a surface, it secretes an oily glue that repels water and contaminants, while adhesive proteins suspended in the lipids cross-link and form strong adhesion to the substrate.
The researchers mimicked this approach by using silicone oil in lieu of the barnacle glue’s lipid-rich matrix. They froze the tape, ground it into powder, and suspended the resulting adhesive microparticles in the oil.
By balancing the hydrophobic and hydrophilic components of the suspension, the resulting paste could function even when flooded with fluid, Yuk says.
The team tested the resulting paste on bloody tissue including pig hearts and rat livers. After applying the paste with light pressure, they found that the oil repels surface fluids and forms a tight seal around the wound within 15 to 30 seconds as the carboxylic acids in the microparticles form immediate hydrogen bonds with tissue. Then, over the next minutes, the adhesive proteins cross-link with one another and the tissue’s surface, strengthening the seal. The approach has no need for UV light, blood coagulation, or extended application of pressure like other existing treatments require.
“There have been many adhesives reported over the years, including some of our own,” says Yu Shrike Zhang, a biomedical engineer at Harvard University who was not involved with the study, “but I don’t remember seeing anything conceptually similar to this.”
“I deal with bleeding patients all the time,” says Rahmi Oklu, an interventional radiologist at Mayo Clinic who was not involved with this study. That the team “tested the material in clinically relevant scenarios suggests that this is more likely to be truly game changing, rather than just thought provoking,” Oklu says.