Development of a multifunctional, injectable biomaterial using hyaluronan as a bioactive nanocarrier

Hyaluronic acid-based biomaterials provide diverse functionality due to the inclusion of multiple bioactive domains within the glycosaminoglycan molecule. This attribute is particularly promising for regenerative strategies to treat central nervous system injury, which is a complex system that requires combinatorial approaches to address different mechanisms. Here, a small molecule inhibitor of transforming growth factor β (TGF-β) signaling, sb431542, and repulsive guidance molecule A (RGMa) antagonist peptide are conjugated to the same hyaluronan-based nanocarrier to simultaneously address multiple aspects of the injury microenvironment. The modified hyaluronan is paired with a thermo-responsive polymeric hydrogel, poloxamer 407, to create an injectable delivery system. Synthesis, characterization, and validation of the injectable platform demonstrates mechanical properties on par with previous scaffolds used in the central nervous system, physiologically relevant release rates of cargo, and the ability to modulate cellular function in a three-dimensional in vitro model. Proof of concept studies in a cervical-level hemisection spinal cord injury animal model indicate increased infiltration of both host axons and astrocytes within the lesion following delivery of the hydrogel. Additionally, tracing of rubrospinal and reticularmotor tracts across the site of injury eight weeks post-injury suggests improvements in connectivity. Overall, this study establishes the utility of combining different biochemical moieties to build heterofunctional nanocarriers and demonstrates that treatments simultaneously addressing multiple aspects of the injury response have the potential to restore connectivity in the central nervous system.