Explant Analysis of Utah Electrode Arrays Implanted in Human Cortex for Brain-Computer-Interfaces

Area of Science:

• Neuroscience
• Biomaterials Science
• Clinical Engineering

Background:

• Brain-computer interfaces (BCIs) offer therapeutic potential for paralysis but require long-term stability for clinical use.
• Factors influencing BCI performance, such as electrode material integrity and host tissue response, are critical but understudied in human implants.

Purpose of the Study:

• To characterize material integrity and tissue encapsulation of explanted human intracortical BCI arrays.
• To identify factors influencing electrophysiological performance and long-term stability of BCI devices.

Main Methods:

• Explant analysis of six Utah arrays (platinum and iridium oxide) from two human participants with varying implantation durations (182 and 980 days).
• Utilized optical microscopy, two-photon microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy.

Main Results:

• Recording quality initially increased then declined, correlating with longer implantation times.
• Arrays implanted longer showed greater tissue encapsulation and material degradation (platinum arrays).
• Iridium oxide coating showed some degradation upon stimulation, but performance was initially unaffected.

Conclusions:

• Both tissue encapsulation and material degradation increase with longer BCI implantation durations.
• These factors correlate with reduced signal amplitude and impedance, compromising electrophysiological performance.
• Development of novel biomaterials is essential to minimize encapsulation and enhance stability for sustained BCI function.