Preparation of Polyurethane-Graphene Nanocomposite and Evaluation of Neurovascular Regeneration.

Graphene, with excellent conductivity can promote the growth and differentiation of neural stem cells (NSCs), but the rigidity has limited its direct application in neural tissue engineering. In this study, waterborne biodegradable polyurethane (PU) was used as the matrix for the graphene nanocomposite materials to make graphene applicable to biocompatible scaffolds. The graphene sheets were observed on the surface of the composites which contained 5 wt % graphene (PU-G5). The nanocomposite retained the positive effect of graphene on cell behavior, while PU was flexible enough for further fabrication. Endothelial cells (ECs) and NSCs cocultured on the nanocomposite became more vascular-like and glial-like without induction culture medium. The specific vascular-related and neural-related gene markers, KDR, VE-Cadherin, and GFAP, were upregulated more than twice as the content of graphene increased (5 wt %). The fibrous capsule of the PU-G5 film group was about 38 μm in thickness in subcutaneous implantation, which was only half that of the graphene-free group. Nerve conduits made of the PU-graphene nanocomposite were found to promote the regeneration of the peripheral nerve in a rat sciatic nerve 10 mm gap transection model. In particular, the regenerated tissue in PU-G5 conduits showed an obvious response peak in the compound action potential (CAP) examination and had a similar CAP wave pattern to that of the normal sciatic nerve. However, such a response was not observed in the PU group. The nerve conduit made of PU-G5 had 72% and 50% enhancement on the numbers of axons and blood vessels of regenerated tissue, respectively. The regenerated area of nerve in PU-G5 was 25% larger than that in pristine PU. Compared with the U.S. Food and Drug Administration (FDA) approved conduit, Neurotube, the regenerated nerve in PU-G5 was 1.7 times more than that in Neurotube. In addition to the fast recovery rate, the ability to regenerate tissue with normal morphology is a significant finding of this study that may lead to clinical applications in the future. PU-graphene nanocomposites thus have potential applications in neural tissue engineering.