Engineered Spider Silk in Core–Shell Multifunctional Fibrous Mat for Accelerated Chronic Diabetic Wound Healing via Macrophage Polarization

Macrophage phenotypic switching from pro-inflammatory M1 to pro-regenerative M2 is impaired in chronic diabetic wounds, leading to excessive reactive oxygen species (ROS) production, poor angiogenesis, and decreased collagen deposition, thereby affecting the healing cascade. Development of multifunctional biomaterial with bioactive compounds to modulate the immune microenvironment and combat ROS, with the potential to facilitate angiogenesis and increase collagen deposition. Here, a novel combination therapy of silk DOPA–crisaborole conjugate (SDC, angiogenic and anti-inflammatory) and eugenol (Eu, antioxidant) has been devised to promote chronic wound healing. The core–shell electrospun fibrous mat has been fabricated with Eu in a polycaprolactone core (PCL-Eu) and SDC in a dextran shell (Dex-SDC), collectively termed Dex-SDC/PCL-Eu. In response to the acidic environment of chronic wounds, the dynamic benzoxaborole–catechol complex between crisaborole and silk DOPA cleaves, releasing crisaborole, while the matrix degradation of Dex-SDC/PCL-Eu over time enables the controlled release of Eu for 12 days. The initial release of crisaborole promotes polarization of M1 macrophages to M2 phenotype by significantly upregulating anti-inflammatory cytokine IL-10 and downregulating pro-inflammatory cytokine IL-6 gene expression in Dex-SDC/PCL-Eu-treated THP-1 cells compared to control. Subsequently, the sustained release of Eu mitigates oxidative damage. Dex-SDC/PCL-Eu fibers facilitate in vitro adhesion, migration, and proliferation of fibroblasts and endothelial cells as well as enhance endothelial tube formation. In the diabetic rat model, the Dex-SDC/PCL-Eu fibers reduce inflammatory granulation tissue and ulceration, while promoting neovascularization, complete re-epithelialization, and well-organized dermis and epidermis formation with uniform collagen deposition. Thus, the developed multifunctional Dex-SDC/PCL-Eu fibrous mat accelerates full-thickness skin wound healing and holds promise for the treatment of chronic diabetic wounds.