Goodbye gauze

Engineering team develops new type of bio-absorbable bandage to help heal wounds faster

The debate between whether it's better to rip off a bandage or peel it back bit by bit may come to an end if a development by an engineering team led by Jeffrey Catchmark, associate professor of agricultural and biological engineering, makes it to the market.

Catchmark's group has been working on a type of bio-absorbable bandage that slowly disappears as a wound heals.

The team's new material is based on cellulose, the same stuff wood is composed of.

Catchmark is quick to say his team isn't the first to try a cellulose-based material for a therapeutic application.

"There are a number of materials out there, including cellulosic materials, similar to the ones that we work with," he says. "What we want to be able to do is put a material on the surface next to where tissue is regenerating. As the material supports that growth, or even enhances it, eventually it goes away."

Catchmark says with traditional bandages, "if you have a really bad wound and you put gauze on it and let it heal, when you take the gauze off, you actually disturb the wound again because the wound heals over the material."

The engineer continues, "So you don't want that. You want a surface that promotes the growth of healthy tissue, but when the tissue is at the right stage, the material essentially vanishes and you have a healthy surface."

With support by Bayer Innovations, the team began investigating a bio-absorbable therapeutic material that could be used for wound care, among other things.

About a year and a half after beginning the work, the Penn State engineers developed a cellulose-based patch infused with a special enzyme that could do the job.

Yang Hu, one of Catchmark's doctoral students, explains that the cellulosic material is produced in a bacteria culture called Arcobacter butzleri. He shows a sample of the material in a beaker, and it looks more like a cup of rice noodles in water than anything resembling wood.

When teamed with a special enzyme, the cellulosic material becomes a bio-absorbable material that can help treat wounds. And as the wound's pH changes while it heals, the patch's enzymes do as well.

Catchmark explains the enzymes are key because they help to break down the cellulose into a harmless byproduct that is absorbed by the body—sugar. And for Catchmark, therein lies the elegance of the team's solution.

"There are a lot of products out there like biopolymers, but it's undetermined what the impacts are of the products. Where do they reside in the body?" he asks. "There are other natural materials that have been used, particularly things like the intestinal lining of pigs, called SIC membranes. The issue with that is they contain a lot of materials from the animal, like growth hormones and other compounds that may or may not be beneficial to a human." "You really want to engineer the materials from the starting point. This covers the bases very nicely. It's bioabsorbable, it can be used as a delivery mechanism, and it's completely pure at the outset."

But creating the enzyme-infused material was just the first hurdle for the team. In order for it to be viable, the engineers had to develop a process that allowed for transport and storage of the material.

Once introduced to the cellulosic material, the enzyme starts to work immediately, Catchmark states. "If you packaged that and shipped it off, by the time you opened it, whether it was a week, two weeks or a month later, there would just be a bag of solution there. So we had to find a way to preserve the enzyme indefinitely."

In addition to figuring out a way to preserve the material, Catchmark wanted to make it easy to use, especially for hospital staff or caregivers who have limited time and training.

"You can't have some complicated process," he says. "They should be able to open up a packet, take the material out, hydrate it with a saline solution or something and apply it."

After experimenting with a number of different preservation methods, the engineers developed a freeze-drying process that accomplished the task.

Hu explains it is a two-step process. First, the raw cellulosic material is freeze dried, producing a thin, parchment-like product called a pellicle.

"That process gives the pellicle a stronger structure to hold the enzyme," Hu says.

The enzyme is then introduced to the pellicle and the combined product is freeze dried again to stop the degradation process.

To use the final product, all that needs to be done is to rehydrate the pellicle.

If you examine the pellicle on the nano scale, you'll find enormous fibrils that can hold a substantial amount of water, Catchmark states. "It can hold a hundred times its weight in water, which is perfect for wound situations where you want to keep the wound surface hydrated and have fluid exchange."

The work has already been patented, and Catchmark says mass producing the pellicles should not be a problem.

"It's just a matter of scaling up the technology. We identified commercial enzymes so we didn't have to develop new enzymes."

The team is already looking at other applications for their work, including regenerating bone and cartilage.

And though Catchmark and his team have been working on the project for more than a year and a half, he still marvels at the solution's inspiration.

"The real solution was a combination of food science—this idea of using freeze drying—and bioenergy technology—for which these enzymes were developed—to solve a health care problem!"

—Curtis Chan