New interdisciplinary research uniting microelectronics and immunology could help pacemakers, sensors, and other implantable devices keep people healthier for longer.
In a paper published today in Nature Materials, a group of researchers led by UChicago Pritzker School of Molecular Engineering (UChicago PME) Asst. Prof. Sihong Wang outlined a suite of molecular design strategies for the semiconducting polymers used in implantable devices, strategies that can reduce the foreign-body response the implants trigger.
In some cases, the immune system might reject lifesaving devices like pacemakers or drug delivery systems. But in all cases, the immune system doing its job will, over time, encase the devices in scar tissue, hurting the devices’ ability to help patients.
“A lot of research groups are making very novel designs of implantable devices, but almost every research group is using a similar model and is facing a similar challenge: long-term implantability,” said UChicago PME postdoctoral researcher Seounghun Kang, a co-first author of the paper.
A polymer – any polymer – is built around a chemical “backbone” with a series of branching side chains building out the rest of the material’s structure. To make polymers that triggered less of an immune response when implanted in live tissue, the team took a two-pronged approach. They both incorporated the compound selenophene into the backbone and added other immunomodulating materials to the side chains.
“Based on these two strategies, we developed these new materials that not only exhibit good biocompatibility, but also maintain the good electrical performance needed for a bioelectronic device,” said co-first author and UChicago PME PhD candidate Zhichang Liu.
Using these materials, the UChicago PME team, including lead first author Nan Li, PhD’23, found as high as a 68% decrease in collagen density – the scar tissue that builds around pacemakers and other devices, reducing their efficiency over time.
Working through scar tissue
For addressing the grand challenge of foreign-body responses for implantable devices, this research complements a hydrogel semiconductor the Wang Research Group created last year to better interface body and machine. Both were funded through an NIH Director’s New Innovator Award Wang received in 2022.
While the hydrogel semiconductor research changed the physical structure of implanted devices, this new work changes their chemistry so that they do not trigger as large an immune response.
“Overall, this comes from our goal of addressing a grand challenge, a universally existing challenge for any kind of implantable device,” Wang said. “When you insert any foreign material into the human body, the immune system will start to attack it. First, this is generating side effects in patients. Second, it is also affecting the long-term stability of the device.”
This means that, over time, the devices that regulate heartbeats, record brain signals, take vital readings, and release insulin and other medications become less efficient and, in some cases, stop working entirely.
“You need the biological signals to be able to efficiently go from the organ to the device to get effective recorded,” Wang said. “But the foreign body response is generating a layer of dense fibrotic tissue, like a scar. That scar layer is insulating the device, encapsulating it to prevent the efficient transport of biomolecules or other types of signals.”
In tests on mice, the team’s new devices recorded, on average, higher-amplitude electrocardiogram (ECG) and electromyogram (EMG) signals after four weeks than the devices based on the existing semiconductor.
The team will next focus on improving the long-term stability of the new materials while continuing to work on ways to decrease the immune system’s response when a foreign body is implanted, Liu said.
"During this research, we also found some different strategies to deal with the foreign-body response, such as reducing the reactive oxygen species,” she said. “That is also part of this very important research.”
For Wang, the ability to better connect electronics and the human body reflects a larger interface – the connection between material science and immunology. He credits UChicago PME’s interdisciplinary approach, where organized by research themes rather than siloed university departments, for allowing creative breakthroughs to flourish.
“This is one of the unique strengths of UChicago PME,” Wang said. “When these two research spaces, these two disciplines, start to interact at a deep level, what kind of new technological frontiers could be generated?”
Citation: “Immune-compatible designs of semiconducting polymers for bioelectronics with suppressed foreign-body response,” Li et al, Nature Materials, April 17, 2025. DOI: 10.1038/s41563-025-02213-x
Funding: This work was supported by the US National Institutes of Health Director’s New Innovator Award (1DP2EB034563), the National Science Foundation (DMR-2105367), the US Office of Naval Research (N00014- 21-1-2266)