Repairing Peripheral Nerves: Is there a Role for Carbon Nanotubes?

Abstract

Peripheral nerve injury continues to be a major global health problem that can result in debilitating neurological deficits and neuropathic pain. Current state‐of‐the‐art treatment involves reforming the damaged nerve pathway using a nerve autograft. Engineered nerve repair conduits can provide an alternative to the nerve autograft avoiding the inevitable tissue damage caused at the graft donor site. Commercially available nerve repair conduits are currently only considered suitable for repairing small nerve lesions; the design and performance of engineered conduits requires significant improvements to enable their use for repairing larger nerve defects. Carbon nanotubes (CNTs) are an emerging novel material for biomedical applications currently being developed for a range of therapeutic technologies including scaffolds for engineering and interfacing with neurological tissues. CNTs possess a unique set of physicochemical properties that could be useful within nerve repair conduits. This progress report aims to evaluate and consolidate the current literature pertinent to CNTs as a biomaterial for supporting peripheral nerve regeneration. The report is presented in the context of the state‐of‐the‐art in nerve repair conduit design; outlining how CNTs may enhance the performance of next generation peripheral nerve repair conduits.

Preparation of carboxylic graphene oxide‐composited polypyrrole conduits and their effect on sciatic nerve repair under electrical stimulation

“…There was the strong polarity bonds interaction between graphene carboxyl group and pyrrole imino group (Figure c), leading to stable conductivity and higher tensile strength of the prepared conduit during the in vivo nerve repair. After the severed transection of the nerve, SCs could dedifferentiate and proliferate on the composite films, and secreted lots of neurotrophic factors, and paved the ways for axon sprouts (Oprych et al, ). On one hand, the axons could elongate along the fiber‐axes; on the other hand, the directions of axons growth and Schwann cells migration were induced by the current direction of exerted ES through C‐GO‐composited PPy‐PLLA conduit, thus there were more axons and Schwann cells parallel to the fiber‐axes in ES & conduit group, leading to their faster migration and extension (Figure e), compared with those in non‐ES conduit group (Figure d).…”

“…However, when the gap of injured sciatic nerve was more than 10 mm, the direct end‐to‐end suture was not suitable anymore, and only autologous nerve grafting was adopted (Das et al, ; Siemionow & Brzezicki, ). Nevertheless, autograft inevitably caused the subsequent damage of graft donor site (Oprych, Whitby, Mikhalovsky, Tomlins, & Adu, ), moreover the available donor site in humans was very limited (Bozkurt et al, ). Recently, some biomaterials have been used in the tissue regeneration, and many natural or synthetic polymers, including collagen, poly‐ l ‐lactic acid (PLLA) and other biomaterials were used to fabricate the scaffold for nerve regeneration (Gu, Ding, Yang, & Liu, ; G. Li et al, ; Wang et al, ).…”

“…However, when the gap of injured sciatic nerve was more than 10 mm, the direct end-to-end suture was not suitable anymore, and only autologous nerve grafting was adopted (Das et al, 2015;Siemionow & Brzezicki, 2009). Nevertheless, autograft inevitably caused the subsequent damage of graft donor site (Oprych, Whitby, Mikhalovsky, Tomlins, & Adu, 2016), moreover the available donor site in humans was very limited (Bozkurt et al, 2015).…”

“…Figure 8c), leading to stable conductivity and higher tensile strength of the prepared conduit during the in vivo nerve repair. After the severed transection of the nerve, SCs could dedifferentiate and proliferate on the composite films, and secreted lots of neurotrophic factors, and paved the ways for axon sprouts(Oprych et al, 2016). On one hand, the axons could elongate along the fiber-axes; on the other hand, the directions of axons growth and Schwann cells migration were induced by the current direction of exerted ES F I G U R E 5 Electrophysiological evaluation of the regenerated nerves in three groups at 4, 8 and 12 weeks of postoperation: (a) the peak amplitude of CMAP recorded in gastrocnemius and (b) the nerve conduction for peer review velocity of the regenerated nerves.…”

Multilayered spraying and gradient dotting of nanodiamond–polycaprolactone guidance channels for restoration of immune homeostasis

“…Carbon-based nanostructured biomaterials can interact with living tissues in a controlled, engineered, and modified manner 4 . They have many allotropes, including carbon nanotubes (CNTs), graphene, and nanodiamonds (NDs) [5][6][7] . CNT scaffolds can increase axon growth speed and anisotropic structure under electrical stimulation and contact guidance to reinforce structural stability with biodegradable conduit materials 8 .…”