Natural Polysaccharide-Based Biomaterials for Skin Wound Healing: Immunomodulatory Mechanisms and Macrophage M2 Polarization.

Efficient cutaneous wound healing relies on the phenotypic transition of macrophages toward an anti-inflammatory, pro-reparative M2-like state. Non-healing chronic wounds are pathologically characterized by the breakdown of this polarization balance. In this review, we synthesize recent research on biomaterials fabricated from naturally occurring polysaccharides with intrinsic immunomodulatory activity, mainly represented by hydrogels that modulate macrophage phenotypic transitions. We first dissect the immune microenvironment of wound healing and elaborate on the core regulatory networks governing M1/M2 polarization, with a particular focus on signaling pathways and metabolic reprogramming. On this basis, we classify pro-M2 natural polysaccharides into mannose-containing and mannose-free categories according to their core structural motifs that mediate immunomodulatory activity, and detail their molecular mechanisms, including pattern recognition receptor engagement (MR, Dectin-1, CD44, etc.) and downstream signaling cascades (STAT6, PI3K/Akt, NF-κB, etc.). Representative polysaccharides such as konjac glucomannan (KGM),