Biohybrid Microelectrode Arrays Improve Biocompatibility

by Sharena Rice, contributing editor

September 2023 issue

For seasoned professionals working with implanted neurotechnologies, the challenge has always been multi-fold: how do you achieve high resolution in neural recordings, minimize scarring, and maintain the structural integrity of brain tissue? One new development at the University of Utah is the biohybrid transition microelectrode array (TMEA). The developers of these biohybrid electrodes were motivated by immune response issues in neural implants and the desire to ensure that an implant’s survival matches the patient’s lifespan. In hopes of reducing inflammation, the team used cultured neurons in polymer shafts to create synapses with the neurons in the brain.

While traditional electrode designs involve rigid shafts, the biohybrid TMEA incorporates a matrix of biohybrid electrodes, constructed from endogenous materials, including neurons. The organic nature of these electrodes both minimizes biocompatibility issues and dramatically reduces the risk of neural damage upon implantation. This addresses one of the industry’s most pressing challenges: maintaining the biological integrity of neural tissue while conducting advanced research.

One of the most compelling aspects of the biohybrid TMEA is its ability to significantly elevate spatiotemporal resolution in recorded neural signals. This enhanced granularity of data can provide actionable insights into neural processes, opening up avenues for more targeted neurotherapeutic interventions. These electrodes are engineered to project axons into brain tissue, establishing synaptic connections that would enable extremely high resolution in readouts. This active participation in neural communication could allow for finer details of neural signals to come into BCI perception stacks, fundamentally enriching the quality of data collected.

In their article preprint, the team at the University of Utah demonstrated that their shafts were strong enough to maintain structural integrity when implanted into the brain of a dead rat, that the neurons cultured in the shafts would indeed project their neurites to the outsides of the shafts while in a tissue phantom neuron-growth enabling hydrogel material, and that the biohybrid TMEAs could be used to record artificial neural signals passed through a buffered solution.

According to study authors Benzoir Ahmed and Yantao Fan, “The foremost challenge we encountered was the extended timeline to achieve functional implantable devices. While microfabrication itself isn’t inherently complex, it’s a time-consuming process. Moreover, the post-implantation period is crucial; axons from our cultured neural cells require time to form synaptic connections. In our animal experiments, not only is the surgical survival essential, but also ensuring that the animals thrive post-operation, allowing these vital connections to mature.”

The biohybrid TMEA offers a logical route of development, but it is important to acknowledge that it is still in its experimental phase. While the preliminary data is encouraging, it needs to advance from this initial feasibility study towards needs validations in live animals and eventually humans. Nevertheless, this technology could very well be an inflection point that allows brain computer interfaces to do much more in decoding nuanced intentions and contents of thought.

The potential applications of biohybrid TMEAs extend to translational research. Similar biohybrid devices could serve as the backbone of next-gen BCI and bioelectronic medicine platforms, driving advancements in neuroprosthetics, targeted drug delivery, and personalized medical treatments. Biohybrid TMEAs may help integrate the nervous system with implantable devices more seamlessly than ever before.