Malva nut residue could help heal wounds, improve medical devices, study shows

Feb. 17 (UPI) -- The humble malva nut, which for centuries has been used to make herbal tea in Southeast Asian countries, could have a much more important future as a sustainable source for medical applications, U.S. researchers say.

The nut, known as Pangdahai or PDH, has a unique ability to expand tremendously when submerged in water. That property sparked an idea to tap it for use as a low-cost, natural and sustainable resource for medical devices that use hydrogels for such things as wound care, regenerative medicine and adhesives for skin-attached sensors and devices, according to scientists at the University of Chicago's Pritzker School of Molecular Engineering.

In a study published Monday in the scientific journal Matter, a university Chemistry Department team led by doctoral candidate Changxu Sun and Professor Bozhi Tian demonstrated that the gooey residue left over from soaking PDH to make an herbal tea for soothing sore throats possesses previously unrealized abilities when processed into an all-natural hydrogel.

The substance can also outperform commercially available gels in transmitting accurate signals while monitoring heartbeats for electrocardiograms via skin-attached patches, they determined.

The findings could have broad implications in the search for sustainable alternatives in the design of many kinds of medical devices that use sticky hydrogels -- especially in the lower-income Southeast Asian countries where malva nut trees are common and locally produced medical resources are rare, Sun told UPI.

"We wanted to see what the potential could be for a new kind of naturally derived hydrogel to benefit healthcare applications," he said.

Hydrogels are widely used in wound care and medical monitoring due to their excellent mechanical properties, electrical conductivity and adhesion.

And they have become a key element in one of the most promising emerging fields in the medical device industry -- flexible electronic products that connect living biological tissues to synthetic electronic systems, such as medical sensors and wearable devices.

Many of the currently available synthetic hydrogels, however, are made from relatively costly and non-degradable materials and have been known to display poor biocompatibility, difficult degradation and weak skin adaptability.

Thus, the search is on for low-cost, organic renewable natural polymers as alternatives, which is where the fruit of the malva tree comes in.

The nut expands to eight times in volume and 20 times by weight when immersed in water, leaving a jelly that is thrown out. That waste material, however, looked and acted like potentially valuable hydrogel to Sun -- a hunch the University of Chicago researchers have now shown to be correct.

"One application for this hydrogel is in regenerative medicine and wound healing," Sun said. "We found the material can actually promote cell migration and the generation of new cells."

Another promising application is bio-signal monitoring, such as ECG patches, which are commonly used in everyday medicine.

"With those devices, if you put the electrode directly onto the skin, you will expect some level of noise, and that requires the use of some interstitial material between the electrode and the skin," Sun said. "Usually synthetic polymers or hydrogels are used for this, but we thought, OK, can we instead use a simple, environmentally friendly material instead?"

The answer turned out to be "yes," and in fact, Sun said the malva nut hydrogel produced an even better "signal-to-noise" ratio than current synthetic versions.

An expert in the field not affiliated with the study, Chi Hwan Lee, a professor of biomedical and mechanical engineering at Purdue University, agreed it is "essential" that sustainable, plant-based materials be developed to supply the quickly expanding use of flexible electronics in biomedicine.

"Traditional electronics rely on non-biodegradable materials that contribute to e-waste and biocompatibility issues, whereas plant-derived biopolymer hydrogels, like the PDH-based material in this study, offer an eco-friendly alternative with excellent flexibility and biocompatibility," he told UPI in an email.

Large-scale production of such materials could be accomplished by optimizing them for existing microfabrication facilities, he added.

While the development of natural hydrogels has made significant progress in recent years, other experts caution there are still some challenges and issues waiting to be addressed.

One of them, according to a Chinese study published last year, is that to produce sufficiently high electrical conductivity and strong adhesion, natural materials generally still must be blended with synthetic materials, which reduces the biodegradability and biocompatibility of the resulting product.

"It is crucial to develop hydrogels based on entirely natural polymeric materials, which are capable of exhibiting excellent properties without relying on other synthetic functional materials," the authors state.

Other drawbacks include their "low performance rates" and high production costs, which makes them uncompetitive with commercial products in the new era of flexible electronics.

All three of those concerns could be answered with the malva nut hydrogel, Sun said, noting it is 100% organic, performs as well or better than synthetic materials and is simple and inexpensive to produce.

And it could especially be a boon to poorer Southeast Asian where the tree grows, such as Thailand, Cambodia, Malaysia, Indonesia and Vietnam.

"They can strategically use the fruits of the tree to help them be self-reliant in their healthcare resources," he said. "In those countries, major cities may have adequate resources, but with villages and small towns, indigenous plants and trees could provide some solutions."