In a new study, the researchers characterised, for the first time, the forces needed for quills to enter and exit the skin. They are also said to have created artificial devices with the same mechanical features as the quills, raising the possibility of designing less-painful needles or adhesives that can bind internal tissues more securely.
The researchers say there is a great need for such adhesives, especially for patients who have undergone gastric-bypass surgery or other types of gastric or intestinal surgery. These surgical incisions are currently sealed with sutures or staples, which can leak and cause complications.
‘With further research, biomaterials modelled based on porcupine quills could provide a new class of adhesive materials,’ said Robert Langer, David H Koch Institute professor at MIT and a senior author of the study, which appears in the Proceedings of the National Academy of Sciences.
Aside from stitches and sutures, doctors sometimes use medical-grade superglue to bind tissue together, said Jeffrey Karp, an associate professor of medicine at Harvard Medical School and a senior author of the paper. However, those glues can be toxic or provoke an inflammatory response.
To create adhesives that would work in the body without producing adverse reactions, the research team is said to have turned to nature for inspiration.
In this case, the researchers considered the North American porcupine, which has around 30,000 barbed quills to defend against predators. Each quill is several centimetres long, with 4mm at the tip covered in microscopic barbs.
The researchers found that despite the difficulty of removing the quills they require very little force to penetrate tissue. Compared with quills with no barbs, the barbed quills require 60–70 per cent less force to penetrate muscle tissue.
The team set out to determine how the quills achieve this combination of penetration and removal.
The researchers found that the tiny barbs at the end of the quill are the key to both ease of penetration and resistance to removal. While the quill is entering tissue, the barbs act to localise the penetration forces, allowing them to tear through tissue fibres much more easily.
The barbs keep the quill from coming out and the force required to pull out barbed quills is four times that required to remove barbless quills.
To explore the possibility of making stronger adhesives, the researchers created a patch with an array of barbed quills on one side. They found that the energy required to remove this patch was 30 times greater than that needed for a control patch, which had quills but no barbs.
The system could also be tweaked so that it penetrates tissue easily but is not as difficult to remove as a porcupine quill, enabling the design of less-painful needles for injections.
The researchers are now working on making quill-inspired adhesives from biodegradable materials, which could be broken down inside the body after they are no longer needed.
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