Table 1.

Material Source-Based Classification of Injectable Hydrogels in Nerve Repair and Regeneration

Hydrogel Source	Base Material	Hydrogel Composition	Results	Reference
Natural biomaterials	HA	Thiolated HA and poly (ethylene glycol)-diacrylate	After 48 hours: Axon growth	[27]
		RGD-modified HA	After 1 week: Differentiation of NPCs within the stroke cavity	[28]
		HA and poly-L-lysine or Nogo receptor antibody	After 3 days: Survival and differentiation of NPCs	[29]
		High molecular weight HA	After 10 days: Reduction of astrocyte activation and scarring	[30]
	Collagen	Collagen and human umbilical cord MSCs	After 8 weeks: Axon regeneration	[31]
	Gelatin	Gelatin with glutaraldehyde	After 7 weeks: Regeneration of nerve axons	[32]
	Chitosan	Chitosan	After 14 days: Promotion of differentiation of dental pulp stem cells in vitro	[33]
		Chitosan	Reduction of oxidative damage	[34]
	Sodium alginate	Sodium alginate	After 4 days: Neurite growth Reduction of oxidative stress	[35]
		Sodium alginate	After 3 weeks: Axon growth	[36]
Synthetic biomaterials	PEG	PEG	After 8 months: Axon regeneration Improvement of function	[37]
	PVA	PVA and HA	After 2 and 4 weeks: Promotion of nerve cell differentiation	[38]
	PHEMA	PHEMA	After 2 and 4 weeks: Differentiation of neural stem cells	[39]
		pHEMA-Lysine	After 2 days: Sustained delivery of neurotrophic factors	[40]
	PHPMA	PHPMA	After 3 months: Axon growth	[41]

Abbreviations: HA, hyaluronic acid; RGD, (Arg-Gly-Asp) peptides; NPCs, neural progenitor cells; MSCs, mesenchymal stem cells; PEG, polyethylene glycol; PVA, polyvinyl alcohol; PHEMA, poly (2-hydroxyethyl methacrylate); PHPMA, poly [N-(2-hydroxypropyl)-methacrylamide].