Spiny headed worms are a clingy lot. They're intestinal parasites with long, cactus-like heads that are perfect for penetrating, and then grabbing hold of, the insides of their host's digestive organs. Now, bioengineers have co-opted these hanger-ons' latching mechanisms for something therapeutic: skin grafts.
These spiny worms (a.k.a. acanthocephalans, a.k.a. "prickly lil' hellspawn") are probably best known for plaguing the intestines of fish, where they attach themselves by virtue of a rather clever, if devious, mechanism. The worm starts by ramming its barbed head into the tissue lining the tunnels of a fish's digestive tract. Once firmly planted in the intestinal wall, the head swells, anchoring itself in place. Voila – the intestinal parasite, it has installed itself.
Where most people see a barbed, weirdly phallic intestinal parasite known for plaguing the insides of fish, bioengineer Jeffrey Karp saw an opportunity. By mimicking the worm's stab-and-swell technique, Karp's team at Brigham Women's Hospital in Boston has created an adhesive patch that could soon replace surgical staples in skin grafts.
The patch, an example of which is pictured here, features microneedle tips that swell when they're exposed to water. If they swell while they're attached to skin, they anchor the patch in place – not unlike the head of a prickly lil' hellspawn (though you'll notice the microneedle tips lack the worm's barbs, a fact that Karp's team says cuts down on patient tissue trauma considerably). The details are recounted in the latest issue of Nature Communications, but the diagram below summarizes them nicely:
According to first author Seung Yun Yang, the adhesion strength of the microneedle tips is roughly 3.5-times that of conventional surgical staples – a figure the researchers determined by attaching and removing the patches from the skin of dead pigs.
"The unique design allows the needles to stick to soft tissues with minimal damage to the tissues. Moreover, when it comes time to remove the adhesive, compared to staples, there is less trauma inflicted to the tissue, blood and nerves, as well as a reduced risk of infection," said Karp in a statement. According to Karp's team's paper, the patch's microneedles are removed by way of the holes they make while penetrating the skin; the swollen microneedles can scrunch down enough to pass through the holes, while causing minimal damage. Once removed, the tips return to their original shape, allowing the adhesive to be used again.
The researchers write that the patch could also be used to deliver subcutaneous medications. What's more, the fact that it can be applied securely to wet tissues means it could be applied during internal surgical procedures.
And to think – all that, inspired by a prickly little intestinal parasite.
The researchers' work is published in the latest issue of Nature Communications.
Top image is an artistic rendition of the spiny headed worm Pomphorhynchus laevis, courtesy of Karp lab