Sequential dual-drug delivery biomimetic hydrogel for temporal orchestration of acute neuroprotection and chronic regeneration in spinal cord injury

Spinal cord injury (SCI) represents a major public health challenge, leading to persistent neurological deficits and disabilities that impose substantial medical and economic burdens on individuals and society. This study introduces a sequential therapeutic strategy aligned with the dynamic pathological progression of SCI. We developed a biomimetic hydrogel integrating hyaluronic acid methacryloyl (HAMA), decellularised extracellular matrix (dECM), edaravone, and sustained-release serotonin (5-HT). This system enables acute-phase damage control and promotes chronic-phase repair. Using in vitro and in vivo models, we demonstrated that edaravone effectively mitigated oxidative stress and inflammation in the acute phase. Specifically, it reduced reactive oxygen species and pro-inflammatory cytokine levels. Furthermore, it suppressed the NF-κB-NLRP3-caspase-1-GSDMD signalling axis in microglia, resulting in decreased pyroptosis. In the chronic phase, the sustained release of 5-HT within the sequential dual-drug delivery biomimetic hydrogel facilitated axonal regeneration and remyelination, supporting functional recovery, as indicated by marked improvements in behavioural scores and electrophysiological assessments. Notably, the combination of edaravone and 5-HT optimised the regenerative microenvironment to promote specific axonal growth. In conclusion, this innovative hydrogel system, tailored to different stages of injury, offers a highly promising comprehensive approach for translational SCI therapy. STATEMENT OF SIGNIFICANCE: Spinal cord injury treatment remains challenging due to temporal pathological progression requiring phase-specific interventions. Current therapeutic approaches typically target single injury phases, limiting overall efficacy. We developed a sequential dual-drug delivery biomimetic hydrogel combining hyaluronic acid methacryloyl with decellularised spinal cord matrix, enabling rapid edaravone release for acute-phase microglial pyroptosis suppression and sustained serotonin release for chronic-phase axonal regeneration. In rat complete transection models, this temporally coordinated strategy reduced inflammatory damage whilst promoting axonal regrowth and remyelination, resulting in improved locomotor and electrophysiological outcomes. This work demonstrates that biomimetic hydrogels with stage-matched drug delivery can address the complex temporal requirements of spinal cord injury repair.