Sticky bandages inspired by geckos鈥� feet could soon be used to seal wounds and close surgeon鈥檚 cuts. Since the bandages would dissolve harmlessly within the body, they could also replace stitches and sutures.
Geckos can walk on walls thanks to nanoscopic bristles, called setae, on the bottom of each foot. Setae produce an intermolecular attraction allowing the gecko鈥檚 foot to stick to almost any surface.
So when of Brigham and Women鈥檚 Hospital in Boston, Massachusetts, and colleagues set out to create a better medical tape for closing wounds and cuts, they decided to use structures similar to those on geckos鈥� feet.
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鈥淎 lot of people were working on gecko-inspired adhesives,鈥� Karp says, but their materials tend to lose stickiness when wet and do not biodegrade, making them unsuitable. Neither have these adhesives been tested on animals鈥� tissues, Karp adds.
Sticky pillars
Karp and colleagues started by creating a polymer called PGSA 鈥� a tough, elastic material that causes little inflammation and biodegrades over a few days or weeks. Then they etched microscopic pillars onto the surface of a sheet made of PGSA, leaving about a million pillars packed into each square millimetre. As with geckos鈥� feet, the pillars鈥� extremely high surface area makes the tape sticky.
Crucially, though, they needed the tape to have a lasting stick, so that it could hold cut tissue together for days or weeks while it heals. As Karp points out, 鈥済eckos can adhere and de-adhere. Otherwise you鈥檇 see a lot of unhappy geckos hanging around on the walls.鈥�
Geckos鈥� feet stick primarily through relatively weak , which attract molecules that are close together. To make the tape form more permanent chemical bonds, Karp and colleagues coated the pillars with a thin layer of dextran, a complex sugar that bonds with the surface of tissue.
鈥淲e tested it on pig intestines 鈥� essentially sausage casings,鈥� Karp says. Compared with simple PGSA, the tape was twice as sticky, withstanding a pull of around 3 to 5 newtons per square centimetre.
Heart of the matter
The tape could be an alternative to today鈥檚 surgical glues, meshes and barriers for closing up cuts and wounds, Karp says. With improvements to make it stickier, it could even be used for very demanding applications, such as binding the surface of the heart, Karp says.
鈥淭he material looks quite practical, as it uses an already adhesive material which is biocompatible,鈥� says of the University of California in Berkeley, US.
鈥淭his is exciting because it shows that we can go beyond nature to engineer designs that never evolved,鈥� adds of Lewis and Clark College in Portland, US. The new tape has only one-tenth the stickiness of geckos鈥� feet, but Autumn says the study 鈥渟uggests that gecko adhesives will have broad application in medicine in the future.鈥�
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