Neural
electrodes are an important part of
brain-machine interface devices that can restore functionality to patients with sensory and
movement disorders. Chronically implanted neural
electrodes induce an unfavorable tissue response which includes
inflammation,
scar formation, and neuronal cell death, eventually causing loss of
electrode function. We developed a poly(
ethylene glycol)
hydrogel coating for neural
electrodes with non-fouling characteristics, incorporated an
anti-inflammatory agent, and engineered a stimulus-responsive degradable portion for on-demand release of the
anti-inflammatory agent in response to inflammatory stimuli. This coating reduces in vitro glial cell adhesion, cell spreading, and
cytokine release compared to uncoated controls. We also analyzed the in vivo tissue response using immunohistochemistry and microarray qRT-PCR. Although no differences were observed among coated and uncoated
electrodes for inflammatory cell markers, lower
IgG penetration into the tissue around PEG+IL-1Ra coated
electrodes indicates an improvement in blood-brain barrier integrity. Gene expression analysis showed higher expression of
IL-6 and MMP-2 around PEG+IL-1Ra samples, as well as an increase in
CNTF expression, an important marker for neuronal survival. Importantly, increased neuronal survival around coated
electrodes compared to uncoated controls was observed. Collectively, these results indicate promising findings for an engineered coating to increase neuronal survival and improve tissue response around implanted neural
electrodes.