The adhesive strategies of marine mussels are key to their survival on wet, wind-swept, and wave-swept surfaces. Given this, mussel tenacity has become a poster child for the wet adhesion needed elsewhere in human technology, particularly in health-care delivery. Mussel adhesion is complex with both chemical and physical underpinnings at multiple length scales. The peculiar catechol-based chemistry of mussel adhesion has inspired a variety of applications ranging from hard and soft tissue repair to drug delivery to magnetic imaging agents. Although the emphasis on new bioinspired materials is inevitable, it should be coupled with the recognition that society is equally well served by the mussel byssus (holdfast) as an indicator of mussel well-being. Byssally interconnected mussel clusters are the basis of mariculture and diverse reef-like intertidal ecologies that resist coastal erosion. Given its exquisite sensitivity to environmental conditions, mussel byssus also serves as an important monitor of pollution and climate change.
To see if the compound worked in live animals, a veterinary surgeon collaborating with Messersmith's team made a 2.5-centimeter incision in the carotid artery of a dog and placed four stitches along the length of that incision to hold it in place. With the stitches alone, the incision bled when the surgeon pressed it. But just 20 seconds after the mussel-based glue was applied, the artery was sealed and didn’t bleed.
More recently, Messersmith’s team began testing its glue on fetal membranes. For the past few decades, surgeons have begun surgically repairing birth defects like spina bifida while a fetus is still in utero. But the process is risky because the surgery risks rupturing the fetal membrane prematurely, sending the mother into premature labor. This can lead to the birth of a tiny, vulnerable preemie.
There are no good adhesives on the market for surgeons to repair such fetal-membrane tears, and that’s the major reason fetal surgery remains risky. But in recent, unpublished experiments in rabbits, Messersmith and colleagues found that after a veterinary surgeon poked a 3.5-mm hole in the animal’s fetal membrane, the new, mussel-inspired glue readily sealed up the puncture. What’s more, without the glue, only 40% of the fetal rabbits survived the surgery, but with the glue, 60% did.
In another recent result that’s in press at Advanced Health Materials, the researchers chemically altered the polyethylene glycol polymer so that the glue would shrink when it hardened. This could counter tissue swelling during surgery, which surgeons say is dangerous. And the fetal surgeons working with Messersmith are testing whether the glue can help reseal the tissue surrounding the spinal cord to repair a serious birth defect known spinal bifida in rabbits.
“It seems like exactly what you want to seal up an artery,” says Emily Carrington, a biologist at the University of Washington’s Friday Harbor Laboratories who studies mussel adhesion and who did not take part in the research. The mussel-inspired glue is ideal, she added, because it is both strong and it has give. “I think it’s very exciting.”