Sprayable phage-cocktail hydrogel promotes diabetic wound healing through macrophage M2 polarization and restoring SP and CGRP signaling axis

Aims Chronic diabetic wounds often fail to heal due to persistent infections and dysregulated immune responses. This study developed a sprayable phage-cocktail hydrogel, a hybrid living material, to provide simultaneous infection control and neuroimmune modulation. Methods A phage-cocktail dressing was formulated using three bacteriophage strains targeting Salmonella enterica, Escherichia coli, and Pseudomonas aeruginosa . These bacteriophages were mixed with a 1% sodium alginate solution to create a hands-free spray-produced dressing. The dressing was evaluated for antibacterial activity, cytocompatibility with 3T3 fibroblasts, and efficacy in healing sterile full-thickness skin wounds in db/db mice. The skin wound recovery, macrophage polarization, calcitonin gene-related peptide (CGRP) and substance P (SP) expression were assessed through histological analysis. Results The dressing achieved approximately 90% antibacterial efficacy while maintaining excellent skin cell cytocompatibility. In db/db mice, the treatment significantly accelerated wound closure (94.2% by day 14), prevented ulceration, and enhanced tissue regeneration. Mechanistic analysis revealed that the dressing induced M2 macrophage polarization and modulated neuropeptide signaling. Specifically, epidermal CGRP sustained M2 macrophages to promote re-epithelialization, while dermal SP facilitated extracellular matrix (ECM) remodeling. Conclusion This sprayable hydrogel integrates antimicrobial efficacy with neuroimmune modulation to accelerate diabetic wound healing. By modulating pathways associated with the SP/CGRP signaling axis, it supports functional ECM remodeling and re-epithelialization while mitigating dermal fibrosis. This layer-specific regulation provides a potent therapeutic framework for achieving regenerative tissue repair in chronic ulcers.