Design of hydrogel biomaterial interfaces for the injured spinal cord

Following spinal cord injury, changes in glial cell behavior and the local extracellular environment combine to produce an inhibitory environment for neuronal regeneration. Hydrogel biomaterials are ideal for treating spinal cord injury as many are injectable and conform to irregular lesion geometries. Numerous studies present novel hydrogel systems modified to control the interface between hydrogels and the injury environment and to mitigate detrimental changes in cellular behavior and extracellular composition. The goal for any spinal cord injury treatment is to promote beneficial cellular behavior and reduce the growth inhibitory nature of the extracellular environment to promote regeneration. Hydrogel systems have been designed to target particular problems affecting regeneration following spinal cord injury: (a) promoting neuronal attachment and axonal growth, (b) promoting remyelination, (c) reducing astrocyte reactivity and glial scar formation, (d) limiting inflammatory response and (e) controlling the release of therapeutic drugs. This review presents a summary of hydrogel systems exhibiting surface characteristics designed to elicit a specific cellular or extracellular response relevant to promoting regeneration. The purpose of this review is to provide insight for researchers deciding what components and characteristics to incorporate into a hydrogel scaffold for the treatment of spinal cord injury.