New Gel Effectively Heals Wounds

By Juliann Schaeffer

A new hydrogel from Brigham and Women's Hospital (BWH) bioengineers has potential wound healing capacities, according to research findings published in an online edition of Advanced Functional Materials.

Ali Khademhosseini, PhD, MASc, senior study author and director of the BWH Biomaterials Innovation Research Center, led the research, along with chemical engineer Nasim Annabi, PhD. According to Khademhosseini, hydrogels in and of themselves are nothing new in biomedicine. But the gels most often used today aren't perfect. One drawback, he notes, is that certain synthetic gels degrade over time, introducing toxic chemicals. And other more natural gels haven't proven strong enough to "withstand the flow of arterial blood through them."

ELP Hydrogel
Brigham and Women's Hospital researchers have found this hydrogel to be comparatively stronger and more flexible than more conventional gels. It's also biocompatible, meaning research has thus far shown it to do no harm to living tissue.

What is the source of these characteristics? The gel, known as a photocrosslinkable elastinlike polypeptide-based (ELP) hydrogel, swells as it's exposed to water, which then gives the material a "jellylike flexibility." This not only more closely mimics the properties of human tissue (such as skin and blood vessels), but the gel's protein content also adds strength.

"When the gel is exposed to ultraviolet light, strong bonds form between the protein molecules. This gives the gel stability without using potentially toxic chemical agents," according to a BWH news article on the new gel.

As its natural components (enzymes) slowly break down the gel after its role in the healing process is through, healthy tissue then takes its place. This is more beneficial than some other synthetic gels, which Khademhosseini says can turn toxic in the body.

Use in Wound Healing
Through their preclinical testing, Khademhosseini says ELP gels are proving to show long-term stability and biocompatibility, which has researchers first looking into the gel's potential for supporting wound repair and functioning as hemostatic material over bleeding wounds.

"The physical and mechanical properties of ELP gels can be tuned by changing the temperature (thermo-responsive) and protein concentration," Khademhosseini expalins. "Moreover, The ELP gels are not harmful to cells and tissue and they can break down by naturally accruing enzymes with no toxic effect."

There are time-saving benefits as well. "The ELP gel forms by using light exposure," he adds. "The photo curable system has the advantage of forming stable gels within seconds to minutes. In addition, photo curing allows for structural and physical control of crosslinking for in vitro and in vivo applications."

With the gel in preclinical testing, Khademhosseini admits the researchers have yet to rule out whether the exposure of the gel to ultraviolet light has harmful effects in tissue. Investigation into that and other safety aspects continues to ensure its safety for human applications.

Issues of cost are also under investigation, as Khademhosseini notes that the costs related to producing ELP on a large scale are currently unavailable.

Applications in Elder Care
Because the aim of this gel is to be easily "photo-cross-linkable" with tunable properties, Khademhosseini says this makes it a great fit for an elder population, and particularly aging skin. "Since the properties of the skin change due to aging, one can tailor the mechanical properties of the gel to match elderly patients," he says.

It's this "tunable" property that allows for customization, providing distinct benefits for elders' skin. "As shown with extensive mechanical testing, the gel can be customized to have different mechanical properties to match the various values observed as people age," he adds. "The material is soft and moist; thus, it displays properties that are compatible with the delicate and thin elderly skin."

These properties could also benefit wound healing in diabetes patients, for whom chronic wounds create unique challenges in healing. "Wounds in elderly patients who are diabetic tend to be chronic wounds that do not heal for many months," says Khademhosseini, noting that the gel can help keep wounds moist and allow them to aerate.

Will the use of the gel speed wound healing? With the research data Khademhosseini has seen thus far, he believes it will. "As [most medical professionals know well], diabetes is one of the most prominent diseases affecting the elderly, and diabetic wounds are notoriously chronic," he says. "Hence, providing a biocompatible gel with numerous attractive features will expedite the healing process."

Yet chronic wounds don't affect only diabetes patients. Therefore, Khademhosseini affirms that the hydrogel's benefits extend beyond those related to diabetes for any type of chronic wound healing. "The gel has numerous advantages such as delivery of healing factors, antimicrobial agents, and a promising exudate uptake ability, all of which account for the potential applications of this gel for chronic wounds," he says.

Other Uses
The researchers may have focused on how this gel can promote wound healing, but it may serve other uses as well, including acting as a scaffold to grow cells or even to stimulate tissue growth. Particularly because the gel's characteristics (its swelling and/or strength) can be tweaked if desired, researchers are investigating how this gel might be used to stop bleeding when combined with silica nanoparticles.

According to a BWH article on the gel, Annabi says the potential applications for this new gel are vast. "This could allow us to immediately stop bleeding with one treatment. We see great potential for use in the clinic. Our method is simple, the material is biocompatible, and we hope to see it solve clinical problems in the future."

— Juliann Schaeffer is a freelance writer and editor based in Macungie, Pennsylvania.