Malva nut in water University of Chicago / Chuanwang Yang
In traditional Chinese medicine, Malva nuts are brewed into tea to soothe sore throats.
Malva nuts can absorb water, expanding up to 20 times their weight — way more than rice or chia seeds.
Changxu Sun, a PhD student at the University of Chicago Pritzker School of Engineering, was fascinated by this unique property.
“You never saw the fruit from a tree expand in that kind of volume,” said Sun, the first author.
The material appeared to have the properties of a natural hydrogel. Hydrogels are soft, water-based materials with various medical uses, from wound care and drug delivery to ECG readings and tissue repair.
In this new work, the researchers revealed that malva nut-based hydrogel could be used for sustainable biomedical applications.
Multi-step process
Malva nuts start in small, oval shapes.
When soaked in water, they expand in volume (8x) and weight (20x), becoming jelly-like. In comparison, rice expands about three times its weight when cooked, and chia seeds swell to 10 times its weight in water.
This leftover jelly is typically discarded after the drink is consumed. The new work revolved around this gelatinous food waste or “goo.”
Creating hydrogels from malva nuts for medical purposes is a multi-step process.
The team blended and centrifuged the nuts to isolate the expanding polysaccharide hydrocolloid, removing the hard shell components (lignins).
The extracted hydrocolloid solution is subjected to freeze-drying, which removes all the water. This process creates a dry, porous, pure malva nut polysaccharide structure, much like a dried sponge.
“If we hydrate those scaffolds again, that becomes a gel,” Sun said.
The process transforms the discarded tea residue into a versatile hydrogel with medical potential.
Shows promise in testing
Hydrogels are soft and water-rich, mimicking human tissue.
Tests were conducted on malva nut hydrogel to assess its effectiveness in medical applications such as wound care and 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,” the author added in the press release.
The team envisions the naturally derived malva nut hydrogel as a valuable new source of medical resources, offering both efficacy and affordability. They believe it has the potential to benefit people worldwide, but Sun is particularly focused on its potential impact in Southeast Asia – the native place where the malva tree thrives.
The hydrogel can provide much-needed, less expensive medical solutions in these nations.
“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.”
Hydrogels have diverse medical applications, including drug delivery, implantable bioelectronics (like pacemakers), tissue repair, and ECG/EKG readings.
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The findings were published in the journal Matter.
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Mrigakshi Dixit Mrigakshi is a science journalist who enjoys writing about space exploration, biology, and technological innovations. Her work has been featured in well-known publications including Nature India, Supercluster, The Weather Channel and Astronomy magazine. If you have pitches in mind, please do not hesitate to email her.
