Coating Topologically Complex Electrospun Fibers with Nanothin Silk Fibroin Enhances Neurite Outgrowth in Vitro

Abstract

Electrospun poly-l-lactic acid (PLLA) fibers are commonly used for tissue engineering applications because of their uniform morphology, and their efficacy can be further enhanced via surface modification. In this study, we aimed to increase neurite outgrowth along electrospun fibers by coating with silk fibroin (SF), a bioinert protein derived from Bombyx mori cocoon threads, shown to be neurocompatible. Aligned PLLA fibers were electrospun with smooth, pitted, and divoted surface nanotopographies and coated with SF by immersion in coating solution for either 12 or 24 h. Specifically, thin-film coatings of SF were generated by leveraging the controlled self-assembly of SF in aqueous conditions that promote β-sheet assembly. For both 12- and 24-h coatings, Congo Red staining for β-sheet structures confirmed the presence of SF coatings on PLLA fibers. Confocal imaging of fluorescein-labeled SF further demonstrated a homogeneous coating formation on PLLA fibers. No change in the water contact angle of the surfaces was observed after coating; however, an increase in the isoelectric point (pI) to values comparable with the theoretical pI of SF was seen. Notably, there was a significant trend of increased dorsal root ganglia (DRG) adhesion on scaffolds coated with SF, as well as greater neurite outgrowth on pitted and divoted fibers that had been coated with SF. Ultimately, this work demonstrated that thin-film SF coatings formed by self-assembly uniformly coat electrospun fibers, providing a new strategy to increase the neuroregenerative capacity of electrospun scaffolds. To our knowledge, this is the first instance of biomedical modification of topologically complex substrates using noncovalent methods.

Longitudinally aligned inner-patterned silk fibroin conduits for peripheral nerve regeneration

“…In this study, we successfully demonstrate patterned SFbased NGCs synthesis and their successful outcomes for PNI repair. Some previous works support our results, demonstrating that longitudinal patterns, for example in the form of fibres, can promote neurite outgrowth [36][37][38]. Mechanical studies demonstrated the optimal Young's modulus of the developed conduits, as well as their kinking and suturability resistance.…”

Electrospun Fiber Scaffolds for Engineering Glial Cell Behavior to Promote Neural Regeneration

“…In addition to changing larger-scale features of the electrospun fibers, such as fiber orientation and diameter, researchers have investigated the impact of adding smaller nanotopographical features, such as pits, divots, and grooves to fibers on nervous system regeneration [ 25 , 127 , 128 , 129 ]. Little has been done to investigate the effect of these nano-scale features on cell differentiation into the Schwann cell lineage or Schwann cell maturation, adhesion, and proliferation.…”

Aligned Fingolimod-Releasing Electrospun Fibers Increase Dorsal Root Ganglia Neurite Extension and Decrease Schwann Cell Expression of Promyelinating Factors

“…Surface wettability was assessed for each fiber type using a Kruss DSA 100 goniometer as described previously (Ziemba et al, 2020) to determine if the inclusion of fingolimod into the electrospun fibers changed the fiber surface chemistry. At least three drops were assessed per replicate.…”