Stretchy implants could stick to arteries to treat high blood pressure

UNIVERSITY PARK, Pa. — High blood pressure, formally known as hypertension, is a leading cause of heart disease in the United States, impacting nearly half of all adults. Approximately one in 10 of these patients experience drug-resistant hypertension that can be difficult to address, but according to researchers at Penn State, tiny devices that gently shock one of the body's most critical arteries could offer effective treatment.

The team developed a new class of 3D-printed bioelectronics made of soft, stretchy materials, as well as an adhesive component that helps the device painlessly stick to biological tissue. The team reported that their new design, which they call CaroFlex and tested in a rodent model, relieved hypertension while causing much less damage to surrounding tissue. They detailed their work in a paper recently published in Device.

According to corresponding author Tao Zhou, Wormley Family Early Career Assistant Professor of Engineering Science and Mechanics, hypertension can traditionally be treated with different drugs and changes to lifestyle or diet. However, drug-resistant hypertension is a pervasive, often chronic condition that does not respond as well — if at all — to conventional treatments.

“For many patients, even taking a combination of three to five medicines doesn’t alleviate their high blood pressure,” said Zhou, who is also affiliated with the Center for Neural Engineering, Huck Institutes of the Life Sciences and Materials Research Institute at Penn State. “In these cases, bioelectronic devices that use electrical signals to modulate the body’s natural response systems offer a promising form of alternative treatment.”

This response system is the baroreceptor reflex, or baroreflex, where the walls of the arteries transporting blood around the body constrict and expand to resolve changes in blood pressure. The action is triggered by specialized nerve endings called baroreceptors, which are found across the body and monitor changes in the stretch of arteries. Many of these receptors are in the carotid sinus, a small area where the carotid artery — a vital pathway that supplies oxygen-rich blood from the lungs to the hands, face and neck — diverges into several branches.

According to Zhou, bioelectronics placed on this sinus can use different frequencies of electricity to stimulate the baroreceptors, safely modulating the reflex and alleviating hypertension. While a few commercially available bioelectronics exist to do just this, they are usually made of rigid metals and plastics that do not integrate well with the body’s soft tissues, among other key issues.

“These devices are usually held in place with stitches,” Zhou said. “These stitches can cause damage to the devices, and more importantly, the tissues they’re integrated with over time, as arteries stretch and shrink to help move blood around the body.”

The team sought to solve these problems by 3D-printing CaroFlex primarily out of hydrogel — a soft, jelly-like material. Conductive hydrogels make up the electrodes that transmit electricity across the device, while adhesive hydrogels offer a strong yet nontoxic adhesive. According to Zhou, this design better matches the mechanics of the tissue in which the bioelectrodes are implemented. Gentle electrical frequencies generated by the electrodes engage baroreflex.

To assess CaroFlex’s performance, Zhou said the team applied it to tissue samples in the lab and examined its physical properties. Testing showed that CaroFlex can be stretched out over more than twice its original size before breaking, while the adhesive film showcased strong and continuous adhesion, even using mixtures that had been stored away for six months.

The team then compared CaroFlex’s electrical performance to traditional bioelectrodes made of platinum, sending electrical currents through each electrode and quantifying the impact the different building materials had on their overall conductivity. CaroFlex stuck to the tissues more closely and with a more reliable electrical connection than traditional electrodes, the researchers reported.

To further test CaroFlex, the team implanted the system into the carotid sinus of rat models. Sensors placed on the rats’ body monitored their blood pressure, allowing the researchers to observe the impact of CaroFlex over a 10-minute testing window. Out of the five different electric frequencies tested, four reduced active blood pressure, lowering readings by over 15% on average. After two weeks, the researchers also found that tissues touched by CaroFlex appeared clean and free of damage or immune response.

Since the design is confirmed to be compatible and functional in living tissue, Zhou said the next step is to fine-tune CaroFlex’s effectiveness and to scale up the approach, culminating in eventual clinical trials to treat hypertension in humans.

“Our lab is actively leading several developments in 3D-printed bioelectronics for use across the body, which is exciting,” Zhou said. “This fabrication approach allows us to design, fabricate and adapt bioelectronics for potential clinical trials and commercial distribution much more efficiently than traditional methods of manufacturing.”

Other co-authors include engineering science and mechanics doctoral candidates Marzia Momin, Salahuddin Ahmed, Jia Sun and Jiashu Ren; Arafat Hossain, electrical engineering doctoral candidate; Xinyi Wang, mechanical engineering doctoral candidate; Li-Pang Huang, research assistant; Umar Farooq, associate professor of nephrology in the Penn State College of Medicine; Basma AlMahood, who earned their degree in physics from Penn State in 2025 and is now a physics doctoral candidate at Michigan State University; and John Bisognano, clinical professor of cardiovascular medicine at the University of Michigan.

This work was supported by the National Institutes of Health and the U.S. National Science Foundation.

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