Fri, 31 Oct 2014
It’s a sticky situation—in the best possible way. By combining proteins that mussels and bacteria use to stick to surfaces, scientists at the Massachusetts Institute of Technology have created a strong new underwater glue. This adhesive could tackle an important challenge in various fields, including surgery, where repairing wet surfaces is essential.
For years, scientists have used marine organisms for insight in producing underwater glues. Water forms a “weak boundary” on surfaces it contacts, which prevents adhesives from attaching, says Dr. Herbert Waite, Professor of Molecular, Cellular, and Developmental Biology at the University of California, Santa Barbara. This becomes a challenge in fields where wet surfaces need to be repaired—marine salvage, dentistry, surgery, and more. But organisms like mussels and barnacles regularly overcome this obstacle, binding easily to wet rocks.
The MIT team turned to these organisms for inspiration—and ingredients. “One of the promises in synthetic biology is to be able to mix and match and optimize biologically based materials,” says Dr. Timothy Lu, an associate professor in MIT’s Synthetic Biology group and an author of the study. Lu and his colleagues combined proteins from two different sources—the feet of mussels, and E. coli bacteria.
By combining proteins that mussels and bacteria use to stick to surfaces, scientists at MIT have created a strong new underwater glue.
A good adhesive has two properties, Waite says: It has to be able to stick to other surfaces, and it also has to bind to itself. DOPA, the protein mussels use to adhere to surfaces, can do both, but its behavior depends upon the conditions of its environment. Mussels use various “tricks” to control their DOPA that aren’t fully understood, Waite says. If you’re not a mussel, it can be hard to manage DOPA’s behavior.
That’s where the second protein helps. Amyloids are also adhesive, water-resistant, and link strongly to one another. Barnacles, algae, and bacteria use them to stick to surfaces. Lu and his team saw an opportunity: “[W]e thought by combining the bacteria with the mussels, we might be able to get some synergistic behavior,” says Lu.
The result was a glue stronger than any other bio-derived or bio-inspired adhesive made to date. Waite, who was not involved with the study, says the results “really impressed” him. The researchers only asked DOPA to work in the form where it adheres to surfaces, he explains, while the amyloid proteins held the glue together. This joint behavior gives the glue its strength.
Lu believes that this is only the beginning. “We only looked at two of the proteins that are involved in mussel adhesion…If we could combine multiple proteins on top of that, maybe we can even get stronger performance,” he says. While the group has been focused on adhesion alone, in the future, the group plans to explore potential underwater and biomedical uses, says Lu.
These biomedical applications could be profound, especially in surgery. Waterproof glues could help seal internal wounds, even when drenched in blood and other fluids. Sutures or staples are currently used to close such holes, but these are hard to affix and can damage tissues, says Dr. Jeffrey Karp, an associate professor at Brigham and Women’s Hospital and Harvard Medical School. Karp, who was not involved in the MIT study.
“There’s a huge unmet need for better adhesives,” says Karp, who is also a co-founder of Gecko Biomedical, which is developing medical adhesives. “There’s really nothing available in the clinic that works well and doesn’t have its drawbacks,” he adds, calling Lu’s team’s work “excellent and very promising.” The next step, Karp says, is to test the glue at larger scales.
To work inside the human body, an adhesive must be biocompatible, or “cell-friendly.” But strong glues are often toxic. “We really don’t have anything that is strong and biocompatible,” says Dr. Pedro del Nido, a specialist in cardiac surgery at Boston’s Children’s Hospital who was not involved with the MIT study.
Lu says his group is interested in testing for biocompatibility and believes that natural sources will yield better biocompatible materials. Looking to nature for advice has served him well so far. “[N]ature has solved a lot of the same problems that we deal with in pretty creative ways…Often times, borrowing upon nature and then applying the tools that we have in our arsenal to improve those properties, I think, is a really powerful way to go.”
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