Characterization of intracortical microelectrode coatings to mitigate scarring and neurodegeneration in vivo

Abstract

Pilot studies assessing the compatibility of the coatings revealed the hypothermic coating was toxic while PCPC coating was deemed suitable for future testing. The uniformity was assessed using scanning and confocal microscopy, demonstrating complete coverage of the probe. The PCPC coating was found to be approximately 300 nm thick using profilometry. Nanoindentation showed that coating was approximately two orders of magnitude softer than uncoated silicon. The coating absorbed water within 3 min and did not exhibit appreciable swelling by scanning electron microscopy. Curcumin appeared to phase separate from the coating and release into the supernatant during the first 2 weeks, at which point the degradation and dissolution rate slowed down. The PCPC polymer demonstrated significant anti-oxidant activity, and curcumin reduced cell death from H2O2. Assessing the in vivo efficacy, the PCPC coating significantly reduced the hole size in males and caused a decreasing trend in GFAP intensity in females. This study demonstrates mild efficacy of the PCPC coating in reducing damage from the electrode as well as scarring and provides a reminder of potential differences in sex responses in nervous system injury.

Intracortical microelectrodes are used for brain-computer interfaces to help paralyzed patients communicate and restore lost limb function following spinal cord injury and stroke. While promising, recording ability of intracortical microelectrodes diminishes over time with a putative cause being neuroinflammation. Both clinical hypothermia and curcumin have demonstrated neuroprotection by targeting a variety secondary injury phenomena. Thus, I aimed to fabricate and characterize intracortical microelectrode coatings: 1) a hypothermic coating consisting of a salt with an endothermic dissolution encapsulated in an upper critical solution polymer and 2) a curcumin coating consisting of the polymer poly(curcumin-PEG1000 carbamate) (PCPC).