Table 2.

Biological cues in conduits for nerve repair

Additive	Type	Material	Gap size	Research time	Application	Ref.
Schwann cell	Cell	Silk–gold nanocomposite	10 mm	18 months	Enhancing myelination of the regenerated nerves	[100]
Neural crest stem cell	Cell	Polycaprolactone nanofiber	15 mm	6/12 weeks	Promoting regeneration across large nerve gaps	[104]
MSC	Cell	EPO-loaded Chitosan	5 mm	4/8 weeks	Accelerating nerve healing process	[103]
ASC	Cell	Cryopolymerized gelatin methacryloyl	10 mm	4/8/16 weeks	Providing a conducive environment for nerve recovery	[46]
OEC	Cell	Collagen–chitosan	15 mm	12 weeks	Promoting axonal regeneration and functional recovery	[101]
CNTF/bFGF	Factor	Collagen	35 mm in minipig	6 months	Repairing 35 mm gap in minipigs	[112]
NGF	Factor	PCLA/silk fibroin	15 mm	12 weeks	Significant improvements in promoting and guiding neurite outgrowth	[113]
GDNF	Factor	GDNF/PCL	5 cm	1 year	Increasing nerve conduction velocity and average area occupied by individual Schwann cells	[114]
Platelet	Cytoplasm	GelMA/PEGDA	10 mm	12 weeks	Promoting hydrogel conduits in peripheral nerve repair	[56]
Melatonin	Drug	PCL	15 mm	12 weeks	Improving recovery efficiency by inhibiting oxidative stress and inflammation	[117]
XMU-MP-1	Drug	GelMA	10 mm	3 months	Promoting the proliferation, migration and neurotrophic factors secretion of Schwann cells	[45]
PSA/HNK-1	Drug	Polyethylene	5 mm	8/15 weeks	Increasing the ratio of myelinated axons/improvements in myelination	[120]
RGFP966	Drug	GelMA	10 mm	3 months	Efficiently bridging a 10-mm gap of rat sciatic nerve by promoting remyelination of axons	[118]