A Better Bandage? Spiny Worm Inspires Stronger Adhesive
Scientists have invented a bio-inspired flexible microneedle adhesive patch that can stick to soft tissues.
CREDIT: Karp lab
Spiny-headed parasitic worms have now inspired new bandages covered with microscopic needles that can stick even onto wet, living tissue, researchers say.
These new adhesives could lead to a stronger, less damaging way of keeping skin grafts in place over wounds, scientists added.
A number of methods to seal wounds exist, but they have drawbacks. Chemical adhesives often release toxic byproducts such as formaldehyde — those that don't often bond only weakly to wet tissues or stick only to specific tissues. Mechanical strategies include stitches and staples, but stitches are difficult to place in tiny spaces and do not work on very soft, thin tissues, and staples can cause significant tissue damage and scarring, and the holes they make are prone to infection.
"There's a huge unmet medical need for better adhesives, to patch leaks in places where they can be catastrophic," said bioengineer Jeffrey Karp, co-director of the Center for Regenerative Therapeutics at Brigham and Women's Hospital in Boston.
Karp and his colleagues looked to nature for inspiration for a new adhesive.
"Nature has figured out ways to overcome significant barriers to achieve strong levels of adhesion in quite challenging environments," Karp told TechNewsDaily.
The researchers based their new bandage on the way a species of spiny-headed worm known as Pomphorhynchus laevis anchors itself within the intestines of fish. The parasite does so by piercing the wall of the intestine with a long, needle-like proboscis and then using muscles to plump up the proboscis' cactus-like tip.
"There's no chemistry involved — it's really only mechanical interlocking," Karp said.
The new adhesive patch is covered with thousands of microscopic cone-shaped needles about 280 microns wide and 700 microns high. In comparison, human hairs are about 100 microns wide on average.
The needles each have a stiff inner core made of polystyrene, which is typically found in plastic bottles, and an outer layer made of a mix of polystyrene and the water-absorbent hydrogel found in diapers. The needle tips can swell up to two or three times their original sizes when wet — as such, when a bandage covered with such needles is pressed against moist living tissue, the needles penetrate the surface and swell up, locking into place.
"The adhesion strength of the tips of the microneedle is more than three times stronger than conventional surgical staples used for skin grafts fixation," said researcher Seung Yun Yang at Brigham and Women's Hospital in Boston.
The microneedles hurt minimally going in, and pulling them off feels akin to peeling off duct tape, Karp said after testing it on his own finger.
"The holes they make are so small that they can close really quickly on removal — within an hour, I couldn't even tell it was once there," Karp said. "The materials are strong enough to remain secure when swollen within tissue, yet weak enough that they can deform and pull out through the initial holes they made. Also, the fact that they swell up to fill the holes they make means that it's harder for bacteria to infiltrate, unlike with staples."
The invention could replace the staples and sutures currently used to keep skin grafts on patients with serious wounds from burns, infection, cancer and other trauma. The researchers could also include therapeutic compounds with the needles.
"These substances may be, for example, antibiotics, growth-promoting compounds, or anti-inflammatory molecules," said researcher Bohdan Pomahac, director of bothBrigham and Women's Hospital's plastic surgery transplantation program and its burn center.
The next step is to create biodegradable versions of this adhesive "that we can use inside the body to seal tissues like intestines," Karp said.
Karp continued that if tests in large animals with these adhesives show improved skin grafts with fewer infections compared to staples," we should be able to advance to the clinic."
The scientists detailed their findings online today (April 16) the journal Nature Communications.