OK nurse, tape him up
Spider-inspired adhesive could replace surgical sutures.
By Nick Carne
Spiders may be scary to some, but you can’t deny they’re clever and at times inspirational.
Already this year Cosmos has reported on, among others, a depth sounder technology developed after researchers copied the specialised optics that give jumping spiders good depth perception, and the potential for the diving bell spider to help industry control toxic or inflammable gases in fluid lines.
Now engineers from the Massachusetts Institute of Technology, US, have unveiled a new adhesive – inspired by the sticky substance spiders use to catch their prey – that binds wet surfaces in a matter of seconds.
From this they have created a double-sided taped which, in tests, bound rat and pig tissues, such as lungs and intestines, in just five seconds. They hope it could eventually replace surgical sutures, which don't work well in all tissues and can cause complications.
"There are over 230 million major surgeries all around the world per year and many of them require sutures to close the wound, which can actually cause stress on the tissues and can cause infections, pain and scars,” says Xuanhe Zhao, senior author of a paper in the journal Nature.
“We are proposing a fundamentally different approach to sealing tissue."
The tape also could be used to attach implantable medical devices to tissues, including the heart, the researchers say.
Forming a tight seal between tissues is difficult because water on the surface interferes with adhesion. Existing tissue glues diffuse adhesive molecules through the water between two tissue surfaces to bind them together, but this takes minutes rather than seconds.
Spider glue, Zhao’s team realised, includes charged polysaccharides that absorb water from the surface of an insect almost instantaneously, clearing a small dry patch for the glue can adhere to.
To mimic this, they designed a material including polyacrylic acid, which is used in nappies (diapers). As soon as their tape is applied it sucks up water, allowing the acid to quickly form weak hydrogen bonds with both tissues.
These bonds and other weak interactions temporarily hold the tape and tissues in place while chemicals embedded in the acid form much stronger bonds covalent bonds with proteins in the tissue.
To make the tape tough enough to last inside the body, Zhao and colleagues incorporated polymers – either gelatin or chitosan (found in insect shells) – that allow the adhesive to hold its shape for long periods of time.
They can control how fast the tape breaks down inside the body by varying the ingredients that go into it.
They are now performing more animal tests and working with doctors to identify additional applications.