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Figure 1. Macrophage polarization and biomaterial influence. The schematic illustrates the polarization of M0 macrophages into M1 and M2 phenotypes in response to distinct biochemical and environmental cues. M1 macrophages, driven by pro-inflammatory stimuli such as IFN-γ, TNF-α, GM-CSF, and LPS, are characterized by the expression of markers including iNOS, CD86, and CD80 and the secretion of inflammatory cytokines (e.g., TNF-α, IL-1β, IL-6). In contrast, M2 macrophages are induced by anti-inflammatory signals such as IL-4, IL-10, IL-13, and TGF-β, expressing markers like CD206, CD209, and FIZZ1, and secreting cytokines (e.g., IL-10, TGF-β) that promote tissue repair and immunomodulation. Engineered biomaterials modulate macrophage polarization: porous scaffolds, carbon nanotubes, and gold nanoparticles enhance M1 polarization, while hydrogels, lipid nanoparticles, micelles, and polymeric nanoparticles promote M2 polarization. Figure created in https://www.biorender.com/ and adapted from Yao et al.^[8,9]. IFN-γ: Interferon-gamma; TNF-α: tumor necrosis factor-alpha; GM-CSF: granulocyte-macrophage colony-stimulating factor; LPS: lipopolysaccharide; iNOS: inducible nitric oxide synthase; TGF-β: transforming growth factor-beta; FIZZ1: found in inflammatory zone 1.