Researchers turn herbal tea ingredient into soft gels for biomedical use

University of Chicago scientists find way to make malva nuts into hydrogels

Scientists have discovered how to take an ingredient used in herbal tea and make it into a jelly-like substance known as a hydrogel, perfect for a variety of biomedical uses. 

In new research from the University of Chicago, published Feb. 17 in Matter, researchers created a malva nut hydrogel for medical uses ranging from wound care to ECG readings. The research doesn’t rely on the rumored health benefits of the nuts—in China, they’re known as a sore throat remedy—but for their ability to swell in water.

Where others saw gooey tea residue, first author Changxu Sun, a PhD student at the UChicago Pritzker School of Molecular Engineering, saw possibility.

“Changxu looked at herbal tea and saw a world of sustainable biomedical applications ready to be built,” said Sun’s advisor, University of Chicago Chemistry Prof. Bozhi Tian. 

Tea treatment

In traditional Chinese medicine, malva nuts are known as Pangdahai, often used in tea as a sore throat remedy, similar to adding ginger or lemon. A sniffling person pops the small dried nut in hot water and watches the magic unfold. 

“Originally, it’s an oval shape one centimeter in width. Once you soak it in the water, it will expand about eight times in volume and 20 times by weight, turning into a gelatinous mass, like a jelly,” Sun said. “After you drink the beverage, you’re left the jelly as a waste. People usually throw that out.”

Sun and Tian saw potential in the gelatinous food waste thrown out with yesterday’s tea. 

“We said, ‘Okay, that's a natural hydrogel,’” Sun said.

Hydrogels are gooey, water-based substances noted for their many applications in health care. As soft and water-loving as human tissue itself, hydrogels are currently already used in wound care, fighting infection and spurring healing beyond what a bandage can do. They’re used in drug delivery systems, implantable bioelectronics like pacemakers, tissue repair, ECG and EKG readings, and other uses.

But turning nuts into medical devices takes more work than just popping them in tea. 

First, the nuts are crushed in a blender and then run through a centrifuge to separate the soft hydrocolloid from the hard, structural lignins that give nuts their shells.

The scientists then freeze-dry the hydrocolloid solution, removing all the water to create a dry scaffolding of pure malva nut polysaccharide. Picture a dried-out kitchen sponge popping back into shape under the kitchen tap. 

“If we hydrate those scaffolds again, that becomes a gel,” Sun said.

Unexplored properties of natural plants

The team began testing their malva nut hydrogel in a variety of medical uses, from wound care to biomonitoring.

“We found it demonstrated superior performance and qualities compared to commercial ECG patches. And then we also applied to the tissue surface in vivo, demonstrating great recording of biosignals,” Sun said. 

“We wanted to show people should shift their attention into the unexplored properties and unexplored resources of natural plants.”

Sun hopes the new, naturally derived hydrogel will provide a new source of powerful but less-expensive medical resources across the globe, but particularly in the Southeast Asian nations where the malva tree grows. 

“They’re low-income countries. Their healthcare systems are always limited by this lack of resources,” Sun said. “Here we have a local, native material that can be used to create valuable healthcare solutions while providing these impoverished areas some economic stability.” 

Citation: “Sustainable Conversion of Husk into Viscoelastic Hydrogels for Value-Added Biomedical Applications,” Sun et al, Matter, February 17, 2025.

Funding: U.S. Army Research Office, National Institutes of Health