Antimicrobial Coating for Intracortical Microelectrodes

Using intracortical microelectrodes to record brain signals can provide valuable insight into brain functions and
treatment plans for neurological disorders. However, microelectrode performance is significantly affected by the
neuroinflammatory response following implantation largely resulting from blood-brain barrier damage and leaky
constituents following implantation. Among these constituents, the role of penetrated microorganisms such as
bacteria on neuroinflammation remains unclear. In contrast to other areas of the body, it is possible for the brain
to respond to very low concentrations of bacteria that do not manifest as systemic infections but may induce
neuroinflammatory response in the brain due to its higher sensitivity. Even with an appropriate sterilization, a
very low level of bacteria can still migrate into the incision site or enter the brain from other internal sources such
as the bloodstream throughout the implantation process. Indefinite delivery of systemic antibiotics has found to
be ineffective in treating low levels of antibiotic-resistant bacteria, and can alter the composition and population
of existing, stable strains of bacteria, that are symbiotic to human health. Thus, the development of a localized
method to modulate bacteria levels may be a critical step towards reducing the neuroinflammatory response
following microelectrode implantation.
Our preliminary data show that neuroinflammatory responses to intracortical microelectrodes can be
exacerbated by bacterial contamination (even at very low abundance); Systemic antibiotics resulted in decreased
recording performance and increased neuroinflammatory response as a significantly more robust
neuroinflammatory response than control was observed by 12 weeks of implantation. Also, live bacteria were
found in the tissue adjacent the implants at 12 weeks post-implantation. Our preliminary data also showed that
titania nanotube arrays (TNAs) prevented bacterial growth and maintained sustained local antibiotics delivery for
>12 weeks. In this proposal, we aim to explore the antimicrobial properties of the TNA coatings in relation to their
effect on bacterial populations and the neuroinflammatory response following intracortical probe implantation as
well as investigate the potential outcomes of local versus systemic antibiotic delivery in controlling resistant
bacteria. A pilot study using Neuronexus recording probes coated with TNAs on their backside will be performed
to evaluate the mechanical integrity of TNA coatings in vivo as well as their effect on recording performance.

Grant Number: 5I21RX004895-02
NIH Institute/Center: VA
Principal Investigator: Jeffrey Capadona