We investigated whether a tube with its inner surface implanted with negatively-charged carbon ions (C(-) ions) would enable axons to extend over a distance greater than 10 mm. The tube was found to support nerves regenerating across a 15-mm-long inter-stump gap. Silicone treated with C(-) ions showed increased hydrophilic properties and cellular affinity, and axon regeneration was promoted with this increased biocompatibility.