A 3D Nerve Guidance Conduit Surface With a Wrinkled Protein Coating Toward Peripheral Nerve Injury Repair

Peripheral nerve injuries (PNIs) resulting in myelin breakdown and axonal degeneration at both the proximal and distal nerve stumps are major clinical concerns that can induce functional loss and diminished quality of life. In biomaterials science, considerable attention has been given to artificial nerve guidance conduits (NGCs), since the engineered tubular structures have the potential to supply a supportive nerve microenvironment to longitudinally align the regenerating axons for bridging the injured nerve sites. Although NGCs may become promising alternatives to nerve autografts, the fabrication approaches available to incorporate directional cues for dictating neuronal behavior and nerve reconnection have been limited to conventional micro/nano-fabrication techniques that are complex and time-consuming due to manual processing steps. Thus, our goal here was to develop a simple manufacturing approach for introducing topographical cues onto NGCs. To achieve this goal, we used an established mechanically actuated silk wrinkling approach to create topographically functionalized surfaces as a potential NGC material platform for guided directional alignment of neurons. We 3D-printed thermo-responsive shape-memory polymer (SMP)-based NGCs that can produce silk fibroin (SF)-wrinkled topographies on the micro and nano-meter length scale. Since SF is a commonly used biomaterial surface coating with excellent neuro-compatibility, we studied the ability to develop NGCs that can autonomously actuate silk wrinkles upon heat-induced contraction of the SMP and evaluated the effects of the topographically functionalized construct on neuronal behavior. Using an immortalized dorsal root ganglion neuronal cell line, we found that the silk-wrinkled conduits displayed high neuronal viability and adhesion compared to uncoated conduits and tissue-culture polystyrene controls. We also found that the wrinkled conduits enabled the neurons to elongate and align parallel to the direction of the wrinkled topography. Longer neurite extension was also observed on the wrinkled conduits compared to their respective controls. These findings demonstrate the potential for functional wrinkled protein coatings to provide directional cues in the fabrication of artificial NGCs for peripheral nerve repair.