Advanced biomaterials for repairing the nervous system: what can hydrogels do for the brain?

Newly developed hydrogels are likely to play significant roles in future therapeutic strategies for the nervous system. In this review, unique features of the central nervous system (i.e., the brain and spinal cord) that are important to consider in developing engineered biomaterials for therapeutic applications are discussed. This review focuses on recent findings in hydrogels as biomaterials for use as (1) drug delivery devices, specifically focusing on how the material can change the delivery rate of small molecules, (2) scaffolds that can modify the post-injury environment, including preformed and injectable scaffolds, (3) cell delivery vehicles, discussing cellular response to natural and synthetic polymers as well as structured and amorphous materials, and (4) scaffolds for tissue regeneration, describing micro- and macro-architectural constructs that have been designed for neural applications. In addition, key features in each category that are likely to contribute to the translational success of these biomaterials are highlighted.