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A novel silk fibroin scaffold containing micro-/nano-fibers promoted dermal regeneration by providing 3D topographic cues.

Micropatterned biomaterials have been used to direct cell alignment for specific tissue engineering applications. However, the understanding of how cells respond to guidance cues remains limited. Plasticity in protrusion formation has been proposed to enable cells to adapt their motility mode to microenvironment. In this study, the authors investigated the key role of protrusion response in cell guidance on patterned silk fibroin films. The results revealed that the ability to transform between filopodia and small lamellipodia played important roles in directional cell guidance. Filopodia did not show directional extension on patterned substrates prior to spreading, but they transduced topographical cues to the cell to trigger the formation of small lamellipodia along the direction of a microgrooved or parallel nanofiber pattern. The polar lamellipodia formation provided not only a path with directionality, but a driving force for directional cell elongation. Moreover, aligned nanofibers coating provided better mechanical support for the traction of filopodia and lamellipodia, promoting cell attachment, spreading, and migration. This study provides new insight into how cells respond to guidance cues and how filopodia and lamellipodia control cell contact guidance on micropatterned biomaterial surfaces.

Engineered scaffolds simultaneously exhibiting multiple cues are highly desirable for neural tissue regeneration. Silk fibroin is a promising natural protein material for nerve repair. However, the lack of specific bioactive cues significantly hinders its application. In this study, the electrospun silk fibroin nanofibers with both biochemical and topographical cues were prepared. The alignment of electrospun nanofibers was optimized by controlling the surface linear velocity of a rotating drum. The silk fibroin nanofibers were further functionalized with laminin through covalent binding, confirmed by immunostaining observation. Cell proliferation and neurite outgrowth assays confirmed that the functionalized aligned nanofibers significantly enhanced directional axonal extensions, providing physical and bioactive cues for neurite outgrowth. Furthermore, the tubular scaffolds with longitudinally aligned microchannels were designed by rolling the functionalized silk fibroin nanofibers. The neurite extension across the lumen of the conduit along the direction of the aligned fibers is apparent. These results highlight the ability of laminin-immobilized silk fibroin nanofibers to enhance neurite outgrowth and to control directional neurite extension, providing a useful approach to construct a regenerative microenvironment for nerve repair materials.

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