Stimulation of macrophage cell lines confined with silica and/or silicon particles and embedded in structured collagen gels.

This article focuses on the development and characterization of composite collagen hydrogels crosslinked with di- or tri-functionalized oligourethanes derived from L-Lysine diisocyanate (LDI) and compounded with silicon-based particles—colloidal silica (Si-O) and silicon nanoparticles (Si-Si)—to modulate macrophage phenotypes in a three-dimensional (3D) microenvironment. The study demonstrates that crosslinking enhances the mechanical strength and degradation resistance of the hydrogels, while incorporation of colloidal silica increases swelling capacity. Both human (THP-1) and murine (Raw 264.7) macrophages encapsulated or seeded on these composites showed good viability and a shift toward an anti-inflammatory M2 phenotype, with Si-Si nanoparticles notably downregulating pro-inflammatory cytokine TNFα and promoting anti-inflammatory cytokines. Subdermal implantation of hydrogel-coated bovine pericardium meshes in rats revealed increased cellular infiltration associated with silica presence, supporting the immunomodulatory potential of these scaffolds. The findings suggest that such silicon-doped, crosslinked collagen gels serve as promising 3D immunomodulatory scaffolds, though further in vivo studies are needed to fully elucidate macrophage-material interactions and broader biological responses.