Substitution-degree-engineered acetylated curdlan Janus dressing: Unidirectional self-pumping for efficient wound...

Chronic wound management requires advanced strategies that integrate exudate control and tissue regeneration. In this study, we engineered a bilayered Janus dressing via electrospinning using strategically acetylated curdlan with tailored degrees of substitution. The dressing consisted of a hydrophobic inner layer (a low-substitution acetylated curdlan) and a hydrophilic outer layer (a high-substitution acetylated curdlan), which synergistically enabled unidirectional fluid transport: rapid exudate absorption (<3 s) through the hydrophilic layer and effective backflow prevention by the hydrophobic layer. This Janus material demonstrated a high swelling capacity (>400%) under physiological conditions, along with suitable mechanical properties (wet-state tensile strength: 5.7 MPa, elongation at break: 55%), ensuring structural integrity during dynamic wound healing processes. In vitro assessments confirmed excellent biocompatibility with no cytotoxicity toward NIH-3T3 fibroblasts or human umbilical vein endothelial cells. In a full-thickness rat wound model, the bilayer dressing significantly accelerated wound closure and enhanced collagen deposition compared with other membrane-treated groups. Immunofluorescence staining revealed a five-fold increase in CD31⁺ vessel density and a significant reduction in CD68⁺ macrophage infiltration by day 14. By combining unidirectional exudate management, mechanical robustness, and immunomodulation, this substitution-degree-engineered polysaccharide-based Janus dressing represents a multifunctional and clinically promising platform for the management of refractory wounds.