Soft Conducting Elastomer for Peripheral Nerve Interface

Abstract

State‐of‐the‐art intraneural electrodes made from silicon or polyimide substrates have shown promise in selectively modulating efferent and afferent activity in the peripheral nervous system. However, when chronically implanted, these devices trigger a multiphase foreign body response ending in device encapsulation. The presence of encapsulation increases the distance between the electrode and the excitable tissue, which not only reduces the recordable signal amplitude but also requires increased current to activate nearby axons. Herein, this study reports a novel conducting polymer based intraneural electrode which has Young's moduli similar to that of nerve tissue. The study first describes material optimization of the soft wire conductive matrix and evaluates their mechanical and electrochemical properties. Second, the study demonstrates 3T3 cell survival when cultured with media eluted from the soft wires. Third, the study presents acute in vivo functionality for stimulation of peripheral nerves to evoke force and compound muscle action potential in a rat model. Furthermore, comprehensive histological analyses show that soft wires elicit significantly less scar tissue encapsulation, less changes to axon size, density and morphology, and reduced macrophage activation compared to polyimide implants in the sciatic nerves at 1 month postimplantation.

Nanoparticle Doped PEDOT for Enhanced Electrode Coatings and Drug Delivery

“…In neural engineering, these coatings are notable for improving recordings from electrodes as small as 7 µm in diameter by lowering thermal noise and increasing the signal‐to‐noise ratio of recorded neural action potentials . Similarly, conducting polymer coatings can greatly increase amount of charge, which can be injected into tissues prior to the buildup of unsafe potentials . These exceptional electrochemical properties have led conducting polymers to be at the forefront of microelectrode design.…”

Soft Electronics Based on Stretchable and Conductive Nanocomposites for Biomedical Applications

“…(E) Reproduced with permission. [ 42 ] Copyright 2019, Wiley‐VCH GmbH. (F) Reproduced with permission.…”

“…Another method that can yield thick conductors is extrusion, which also allows for the formation of stretchable conductive fibers for implants (Figure 1F). Thermoplastic elastomers are often used in extrusion processes, with the conductor either being mixed into the elastomer [ 42 ] or coated on top of the elastic fiber afterward. [ 43 ] Extruded implantable conductors have had diameters in the 100–200 µm range and sheet resistances (with respect to the diameter) of 10–100 Ohm sq −1 (for more details on stretchable fiber implants see Section 3).…”

“…[ 106–108 ] New nanocomposite materials incorporating gold coated silver NWs, platinum black, PEDOT:PSS coated silver nanoparticles or carbon nanotubes try to combine high conductivity and charge transfer capacities with low stiffness and high biocompatibility. [ 42,109–113 ]…”

Preparation of Multiwall Carbon Nanotubes Embedded Electroconductive Multi-Microchannel Scaffolds for Neuron Growth under Electrical Stimulation

“…Carbon nanotubes (CNTs) are increasingly used as biomedical material due to their excellent mechanical and electrical properties and high stability [6,7]. CNTs can endow synthetic composites with good biocompatibility [8,9], shape memory, mechanical properties [10], photothermal conversion ability, antibacterial properties [11], and conductivity which can simulate electrical conduction to guide the growth of nerve cells and promote myelination [12,13], providing a new strategy for clinical peripheral nerve regeneration and functional reconstruction. However, CNTs were usually used as a component of composite materials, due to cytotoxicity of high concentration of carbon nanomaterials [7].…”