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Insole is step forward in healing diabetic foot ulcers

(Credit: Getty Images)

Researchers have developed a shoe insole that could help make the healing process more portable for the 15 percent of Americans who develop ulcers as a result of diabetes.

Diabetes can lead to foot ulcers that patients don’t feel or notice until it’s too late. Because they can’t heal on their own, 14 to 24 percent of diabetics in the US who get ulcers end up losing toes, a foot, or a leg.

“One of the ways to heal these wounds is by giving them oxygen,” says Babak Ziaie, professor of electrical and computer engineering at Purdue University. “We’ve created a system that gradually releases oxygen throughout the day so that a patient can have more mobility.”

insole for diabetic ulcers
A new shoe insole technology could help diabetic ulcers heal better while walking. (Credit: Purdue/Kayla Wiles)

Flexible silicon

Diabetic ulcers commonly result from high blood sugar damaging nerves, which takes away feeling from the toes or feet.

Without the ability to feel pain, hits and bumps tend to go unnoticed and skin tissue breaks down, forming ulcers. A lot of sugar in the bloodstream, along with dried skin as a consequence of diabetes, further slow the ulcer healing process.

“We typically treat ulcers by removing devitalized tissue from the surface of the wound, and by helping the patient to find ways to take the weight off the affected foot,” says Desmond Bell, a podiatrist in wound management and amputation prevention at the Memorial Hospital in Jacksonville, Florida, and the founder of the Save a Leg, Save a Life Foundation.

“The gold standard for treating an ulcer is a patient wearing a total-contact cast, which provides a protective environment for the foot. If we could test how well this insole delivers oxygen to the wound site from within the cast, then this could be a way of aiding the healing process,”¬†Bell says.

As reported in Materials Research Society Communications, researchers used lasers to shape silicone-based rubber into insoles, and then create reservoirs that release oxygen only at the part of the foot where the ulcer is located.

“Silicone is flexible and has good oxygen permeability,” says Hongjie Jiang, a postdoctoral researcher in electrical and computer engineering. “Laser machining helps us to tune that permeability and target just the wound site, which is hypoxic, rather than poison the rest of the foot with too much oxygen.”

‘Wound profile’

Simulations show the insole can deliver oxygen at least eight hours a day under the pressure of someone weighing about 53-81 kilograms (117-179 pounds). But the insole can be customized to take on any weight, the researchers say.

The team envisions a manufacturer sending a patient a pack of pre-filled insoles customized to his or her wound site, based on a “wound profile” obtained from a doctor’s prescription and a picture of the foot.

“This is mass-customization at low cost,” says Vaibhav Jain, a recent graduate from Purdue’s mechanical engineering master’s program and a current research associate in electrical and computer engineering.

Next, the researchers want to create a way to 3D print the whole insole, rather than printing a mold first and then laser-machining a pattern. They also plan to test the insole on actual diabetic ulcers, to further gauge how well they advance the healing process.

“We’re wanting to bring this technology to the user by addressing whichever technicalities would be required to simplify the manufacturing flow,” Jain says.

A patent is pending on the insole technology and the team is currently seeking corporate partners. The NextFlex PC 1.0 Project funded the work.

Source: Purdue University