The promise of brain implants to help patients with paralysis, epilepsy and other neurological disorders is being complicated by an unexpected culprit: bacteria from the gut that can invade the brain after implantation, researchers have discovered.
Scientists at Case Western Reserve University recently found that when medical devices are implanted in the brain, they can create a breach in the blood-brain barrier that allows bacteria—some originating from the intestines—to enter brain tissue. This bacterial invasion contributes to inflammation that reduces the effectiveness of the implants over time.
“This is a paradigm-shifting finding,” said George Hoeferlin, the study’s lead author, who conducted the research as a biomedical engineering graduate student at Case Western Reserve. “For decades, the field has focused on the body’s immune response to these implants, but our research now shows that bacteria—some originating from the gut—are also playing a role in the inflammation surrounding these devices.”
The study, published March 2025 in Nature Communications, could transform how brain implants are designed and maintained, potentially making them more effective for patients who rely on this technology to restore neurological function.
Brain-machine interfaces are increasingly being used to help patients with conditions like paralysis control external devices or even their own limbs. But maintaining long-term reliability has been a significant challenge. Until now, researchers primarily blamed the body’s immune response for the gradual decline in device performance.
The investigation examined the presence of bacterial DNA in the brains of mice implanted with microelectrodes. Researchers found that devices treated with antibiotics had reduced bacterial contamination and improved performance—at least temporarily. Long-term antibiotic use, however, proved detrimental.
“Understanding the role of bacteria in implant performance and brain health could revolutionize how these devices are designed and maintained,” said Jeff Capadona, Case Western Reserve’s vice provost for innovation, the Donnell Institute Professor of Biomedical Engineering and senior research career scientist at the Louis Stokes Cleveland VA Medical Center, who led the study.
Using advanced sequencing techniques, the team identified bacterial DNA in brain tissue surrounding the implants, with many sequences matching bacteria typically found in the intestines. In mice treated with antibiotics to reduce gut bacteria, the implants initially performed better, with less inflammation around the devices.
The research offers a new perspective on why brain implants often fail over time. The findings suggest that the trauma of implantation creates a passage for bacteria to enter the brain, triggering inflammatory responses that interfere with the device’s ability to detect neural signals.
Even more concerning, some of the bacteria found in the brain have been previously linked to neurological diseases, including Alzheimer’s, Parkinson’s and stroke.
“If we’re not identifying or addressing this consequence of implantation, we could be causing more harm than we’re fixing,” Capadona added. “This finding highlights the urgent need to develop a permanent strategy for preventing bacterial invasion from implanted devices, rather than just managing inflammation after the fact. The more we understand about this process, the better we can design implants that work safely and effectively.”
The team also examined the fecal matter of a human subject implanted with a brain device and found similar bacterial patterns, suggesting this isn’t just a laboratory phenomenon but potentially a clinically relevant issue that could affect patients with neural implants.
“Through our strong translational pipeline between CWRU and the VA, we are now investigating how this discovery can directly contribute to safer, more effective neural implant strategies for patients,” said Bolu Ajiboye, the Robert and Brenda Aiken Professor in biomedical engineering at the Case School of Engineering and School of Medicine and scientist at the Cleveland VA Medical Center.
In their research, the scientists not only identified the bacterial invasion but also observed how it disrupted the gut-brain axis, contributing to reduced microelectrode performance. While short-term antibiotic treatment improved implant function, long-term use was associated with neurodegeneration pathways and worsening performance—highlighting the need for more targeted approaches.
The discovery opens potential new avenues for improving brain implant technology, including designing antimicrobial coatings for devices or developing preventive treatments that specifically target problematic bacteria without disrupting beneficial microbes.
Capadona’s lab is now expanding the research to examine bacteria in other types of brain implants, such as ventricular shunts used to treat hydrocephalus, an abnormal buildup of fluid in the brain.
As brain implant technology continues to advance, this research provides a critical new understanding of the biological challenges these devices face—and potentially how to overcome them.
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