Biofunctionalized silk fibroin nanofibers for directional and long neurite outgrowth

Abstract

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.

Silk Fibroin: An Ancient Material for Repairing the Injured Nervous System

“…SF fibers can be gathered in various collectors to make 2D and 3D highly arranged mats or weaves of different shapes. This method has the potential to fabricate highly arranged structures to guide cells and push them toward further proliferation, differentiation, and adhesion and to be used as conduits for axonal guidance and neuronal regeneration [44,99,100]. A main issue is the hardship of constructing structured 3D scaffolds to fill spatial defects in the nervous tissue [101].…”

“…The cell attachment properties of SF biomaterials can be further improved by refining the residual negative charge of silk fibers [61]. Due to the lack of bioactive molecules in SF, the functionalization of this biomaterial with ECM proteins (such as fibronectin, laminin and collagen), ECM-adhesive peptides (such as the peptide sequences Ile-Lys-Val-Ala-Val; IKVAV and Arg-Gly-Asp; RGD) and growth factors (such as nerve growth factor and fibroblast growth factor [100]) have been applied in numerous studies.…”

“…Laminins are composed of various α, β, and γ chains and are strongly bioactive molecules found in the basal lamina with an important role in cellular adhesion and differentiation. In silk fibers, the treatment with laminin has been found to promote cell migration, proliferation, nerve regeneration, and neurite outgrowth with considerable axonal extensions [100]. The laminin on the surface of electrospun SF mats has been coated to improve the proliferation, differentiation, and survival of neuronal progenitor cells [161].…”

Photothermal Response Induced by Nanocage-Coated Artificial Extracellular Matrix Promotes Neural Stem Cell Differentiation

“…During in vitro culture, three-dimensional structures, such as grid patterns of extracellular matrix protein, increase NSC differentiation into neurons while decreasing differentiation into glial cells [ 14 ]. Recent stem cell studies demonstrated that NSCs respond strongly to the nanoscale topography of the matrix environment such as nanofiber and 3D-printed structures [ 15 , 16 , 17 , 18 , 19 ]. However, many previous studies have used limited types of nanoscopic geometries (e.g., nano-wires and nano-needles) as optimal artificial extracellular matrices (aECMs) [ 20 ], which limits control over differentiation into specific cell types.…”

Advanced Materials to Enhance Central Nervous System Tissue Modeling and Cell Therapy

“…[ 160 ] Additionally, naturally derived silk fibroin functionalized with laminin displayed enhanced and unidirectional neurite outgrowth. [ 161 ] Carbon nanotubes have been considered for guiding neuronal axon growth as well and demonstrate biocompatibility. [ 162 ] For NSC transplantation, a PEG‐4MAL based polymer that used affinity based binding of laminin to N‐terminal agrin (NtA) displayed higher bioactivity compared to alternative strategies to incorporate laminin into the synthetic polymer.…”