The hooks a parasitic worm uses to penetrate its host's intestines have inspired researchers to develop an adhesive patch that adheres better to wet, soft tissue, improving the bandages used on surgical wounds and to keep skin grafts in place.
The spiny-headed worm, Pomphorhynchus laevis, hooks tiny, sharp barbs on its proboscis into the intestinal walls of its host, a fish. Then the worm swells up its proboscis, which looks a lot like a cactus, to lock the needle-sharp hooks in place as it feeds. Jeffrey Karp, associate professor at Harvard Medical School (HMS) and co-director of the Center for Regenerative Therapeutics at Brigham and Women's Hospital (BWH), headed a team that invented the adhesive patch.
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The Karp Lab has invented a flexible adhesive patch covered with microneedles that adheres well to wet, soft tissues, but does not cause damage when removed. (Source: The Karp Lab/Brigham and Women’s Hospital)
When wet, the tips of each tiny microneedle in the patch, which measures 2 cm x 2 cm, swell up and interlock with the wound tissue to hold the patch in place, causing very little damage. The microneedles are made of plastic, each with a stiff core and a tip that expands when wet. They don't need much force to penetrate wound tissue, they keep continuous contact with the wound's surface, and their adhesion strength remains high as long as they are swollen with liquid. Adhesion strength is about 3.5 times the adhesion strength of the staples normally used in fixing skin grafts, the team says in an article detailing their research in Nature Communications (payment or subscription only).
When fluid is withdrawn the process is reversed, and the patch can be easily removed from the wound with much less trauma to tissue, blood, and nerves, as well as much lower risk of infection, said Karp in a press release. You can watch a video demonstration below showing how the swellable microneedle patch works.
The team sees the patch as an alternative to the staples and sutures that are used to keep skin grafts on wounds caused by cancer, infection, and burns, as well as other types of trauma to the skin. The technology may also be used for delivery of drugs and other kinds of therapy into wounds, as well as during various surgical procedures.
Research headed by Karp in the Karp Lab includes new types of drug delivery and release systems, diagnostic nano-devices and micro-devices, and advanced biomaterials and tissue engineering. It has invented a sticky adhesive tape, inspired by geckos, that can be easily removed from the fragile skin of newborn babies and elderly patients without damage. Lab researchers are currently working on a new design for medical needles and adhesive patches modeled after a porcupine's quills, which are easy to insert but difficult to remove.
Other members of the team include Seung Yun Yang, HMS research fellow in medicine at BWH; Bohdan Pomahac, HMS associate professor of surgery at BWH and director of the hospital's Plastic Surgery Transplantation and Burn Center; Eoin O'Cearbhaill, post-doctoral student at BWH; Geoffroy Sisk, plastic surgeon at BWH; Kyeng Min Park, post-doctoral student at Harvard University; Woo Kyung Cho, post-doctoral student at MIT; Martin Villiger, post-doctoral student at Massachusetts General Hospital; and Brett Bouma, associate physicist in the Wellman Center at Massachusetts General Hospital. The study was funded by the National Institutes of Health's National Institute of General Medical Sciences and the National Research Foundation of Korea.
Chuck, I know it seems counterintuitive, but the tiny plastic hooks are so small and flexible/soft that they're supposed to be painless. The whole point of the device is adhering to wounds while not causing pain and then being easy to take off when not engorged with fluid.
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The first ASME Additive Manufacturing + 3D Printing Conference (AM3D) will be co-located with the organization's International Design and Engineering Technical Conferences (IDETC) and Computers & Information in Engineering Conference (CIE), Aug 2-5 in Boston.
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