Clinical implantation of intracortical microelectrodes has been hindered, at least in part, by the perpetual inflammatory response occurring after device implantation. The neuroinflammatory response observed after device implantation has been correlated to oxidative stress that occurs due to neurological injury and disease. However, there has yet to be a definitive link of oxidative stress to intracortical microelectrode implantation. Thus, the objective of this study is to give direct evidence of oxidative stress following intracortical microelectrode implantation. This study also aims to identify potential molecular targets to attenuate oxidative stress observed postimplantation. Here, we implanted adult rats with silicon non-functional microelectrode probes for 4 weeks and compared the oxidative stress response to no surgery controls through postmortem gene expression analysis and qualitative histological observation of oxidative stress markers. Gene expression analysis results at 4 weeks postimplantation indicated that EH domain-containing 2, prion protein gene (Prnp), and Stearoyl-Coenzyme A desaturase 1 (Scd1) were all significantly higher for animals implanted with intracortical microelectrode probes compared to no surgery control animals. To the contrary, NADPH oxidase activator 1 (Noxa1) relative gene expression was significantly lower for implanted animals compared to no surgery control animals. Histological observation of oxidative stress showed an increased expression of oxidized proteins, lipids, and nucleic acids concentrated around the implant site. Collectively, our results reveal there is a presence of oxidative stress following intracortical microelectrode implantation compared to no surgery controls. Further investigation targeting these specific oxidative stress linked genes could be beneficial to understanding potential mechanisms and downstream therapeutics that can be utilized to reduce oxidative stress-mediated damage following microelectrode implantation.

The smooth surface structure of intracortical microelectrodes implanted within the nanometer‐scale architecture of brain tissue may contribute to the foreign body response. Here, the neuroinflammatory response to nanopatterning surface grooves etched directly on nonfunctional Michigan‐style microelectrodes is explored. Rats implanted with nanopatterned silicon microelectrodes are compared to smooth control implants to observe the effects the grooves have on neuroinflammation. Histology and real‐time PCR at 2 and 4 weeks postimplantation quantify glial cell reactivity and activation, inflammation, oxidative stress, and neuronal survival. Histological observations of glial cells and blood–brain barrier permeability do not show appreciable differences between the nanopatterned and control implants. However, silicon microelectrodes with nanopatterned grooves have more high mobility group box 1 (HMGB1) gene expression at 2 weeks and less nitric oxide synthase (NOS2) gene expression at 4 weeks compared to control surfaces. Control samples have increased NOS2, HMGB1, and tumor necrosis factor gene expression from 2 to 4 weeks, while nanopatterned implants have significant decrease in CD14 gene expression from 2 to 4 weeks. Collectively the results indicate that etching nanopatterned grooves do not reduce histological markers of neuroinflammation compared to control implants, but gene expression results encourage further investigation.

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