Materials approaches for modulating neural tissue responses to implanted microelectrodes through mechanical and biochemical means

Abstract

Implantable intracortical microelectrodes face an uphill struggle for widespread clinical use. Their potential for treating a wide range of traumatic and degenerative neural disease is hampered by their unreliability in chronic settings. A major factor in this decline in chronic performance is a reactive response of brain tissue, which aims to isolate the implanted device from the rest of the healthy tissue. In this review we present a discussion of materials approaches aimed at modulating the reactive tissue response through mechanical and biochemical means. Benefits and challenges associated with these approaches are analyzed, and the importance of multimodal solutions tested in emerging animal models are presented.

A critical review of cell culture strategies for modelling intracortical brain implant material reactions

“…It must be noted that the damage caused by electrode insertion cannot be completely eliminated. To date, no combination of these strategies has been successful in substantially mitigating implantation trauma [12,57,58]. Recently, Schwarz et al [54], reported microelectrode recordings from rhesus monkeys lasting for over four years.…”

“…Additionally, there have been reports of entire electrode arrays failing within a few months of implantation [18]. The exact causes of electrode or device failures in the current literature are often not reported, however the majority of the literature points towards biological events as the principle cause of progressive electrode failure [9,12,16,17].…”

“…The factors leading to electrode failure in vivo are multifaceted and complex [12], as they can result from material failure (e.g. electrode delamination), mechanical failure (e.g.…”

“…A core issue that currently hinders the widespread application of penetrating intracortical electrodes in biomedical microdevices is the high rate of failure in chronic settings [12]. Electrode failure can be defined as any event which results in signal-to-noise ratio (SNR) that renders the signal meaningless, an impedance value that breaches the safe charge injection limits of the electrode material [13e15], or any event that disables the electrode.…”

State-of-the-art MEMS and microsystem tools for brain research

“…Tissue response and structure size The adverse tissue response to implantable neurotechnology has been an ongoing area of active research and is reviewed elsewhere (Jorfi, Capadonia 2015) 86 . Important components of the adverse response have been studied, including insertion trauma [87][88][89] , the intrinsic foreign body response 90,91 , and straininduced damage from mechanical mismatch [92][93][94] .…”