L-arginine-loaded microneedle patch enhances diabetic wound healing by regulating macrophage polarisation and mitochondrial homeostasis

Excessive oxidative stress and dysregulated macrophage polarization-characterized by M1/M2 imbalance-drive chronic, persistent inflammation and represent key pathological mechanisms underlying impaired tissue repair in diabetic wounds; however, therapeutic strategies targeting both these processes remain limited. L-arginine (L-Arg) shows therapeutic potential through its antioxidant properties and ability to promote M1 macrophage polarization. Nevertheless, the mechanisms by which L-Arg regulates mitochondrial homeostasis to exert antioxidant effects remain unclear. Moreover, its clinical translation is hindered by poor retention, inadequate tissue penetration and damage induced by hypertonicity, thereby necessitating the development of innovative delivery systems. To address these limitations, we developed an L-Arg-loaded microneedle (L-Arg-MN) patch for controlled delivery. Our findings demonstrate that L-Arg alleviated hydrogen peroxide (H₂O₂)-induced cellular damage through activation of the Kelch-like ECH-associated protein 1 (KEAP1)-nuclear factor erythroid 2-related factor 2 (Nrf2)-heme oxygenase-1 (HO-1) pathway, boosting antioxidant enzyme (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px)) and lowering malondialdehyde (MDA) levels. Mechanistically, L-Arg maintained mitochondrial homeostasis by upregulating peroxiredoxin 1 (PRDX1) expression, restoring mitochondrial membrane potential and enhancing adenosine triphosphate production. Furthermore, L-Arg suppressed M1 macrophage polarization and promoted M2 polarization through PRDX1-mediated mitochondrial metabolic pathways. In models of diabetic wounds, the L-Arg-MN patch markedly enhanced the wound healing process, accelerated wound closure, reduced concentration of reactive oxygen species (ROS), enhanced granulation tissue, collagen formation and increased M2 macrophage infiltration. This study elucidates how L-Arg reduces oxidative stress and enhances M2 macrophage polarization by regulating mitochondrial metabolism through the PRDX1 pathway. By integrating the metabolic and immunomodulatory properties of L-Arg with advanced drug delivery technology, the L-Arg-MN patch presents an innovative and efficient approach to treating diabetic wounds.