Advancing neural regeneration via adaptable hydrogels: Enriched with Mg2+ and silk fibroin to facilitate endogenous cell infiltration and macrophage polarization

Peripheral nerve injury is a complex and challenging medical condition due to the limited ability of nerves to regenerate, resulting in the loss of both sensory and motor function. Hydrogels have emerged as a promising biomaterial for promoting peripheral nerve regeneration, while conventional hydrogels are generally unable to support endogenous cell infiltration due to limited network dynamics, thereby compromising the therapeutic outcomes. Herein, we present a cell adaptable hydrogel containing a tissue-mimetic silk fibroin network and a dynamically crosslinked bisphosphonated-alginate network. The dynamic network of this hydrogel can respond to cell-generated forces to undergo the cell-mediated reorganization, thereby effectively facilitating the rapid infiltration of Schwann cells and macrophages, as well as the ingrowth of axons. We further show that the magnesium ions released from the hydrogel not only promote neurite outgrowth but also regulate the polarization of macrophages in a sequential manner, contributing to the formation of a regenerative microenvironment. Therefore, this hydrogel effectively prevents muscle atrophy and promotes the regeneration and functional recovery of nerve defects of up to 10 mm within 8 weeks. The findings from this study demonstrate that adaptable hydrogels are promising inductive biomaterials for enhancing the therapeutic outcomes of peripheral nerve injury treatments.