Biopolymer-Nanotube Nerve Guidance Conduit Drug Delivery for Peripheral Nerve Regeneration

Peripheral nerve injuries account for roughly 3% of all trauma patients with over 900,000 repair procedures annually in the U.S. Of all extremity peripheral nerve injuries, 51% require nerve repair with a transected gap. The current gold-standard autograft repair has several associated shortcomings, while engineered constructs typically offer suboptimal results only suitable for short gaps. In order to achieve enhanced peripheral nerve regeneration and greater functional recovery, we have developed a biodegradable, chitosan-based nerve guidance conduit (NGC) with aligned microchannel porosity and halloysite nanotubes for the sustained release of 4-Aminopyridine (4AP), a small molecule drug that promotes nerve conduction and neurotrophic factor release. In vitro studies characterized the polymer NGC system and confirmed the sustained release of 4AP. Human Schwann cells showed a dose-dependent elevation of critical proteins including nerve growth factor (NGF), myelin protein zero (P0), and brain derived neurotrophic factor (BDNF). When treated with 10 µg/mL 4AP, NGF, P0, and BDNF showed 128.58±0.57%, 310.75±11.92%, and 170.94±4.43% increases over no-drug control groups, respectively. When tested in vivo using a critical-size (15 mm) rat sciatic nerve transection model, the results of functional walking track analysis, morphometric evaluations of myelin development, and histological assessments of various markers confirmed the equivalency of the drug-conduit repair to autograft controls. At 8 weeks post-operative, the sciatic functional index (SFI) of autograft (-44.89±4.73) was not statistically different from drug-conduit (-45.12±4.45), while myelin thickness (G-ratio) evaluations also showed no statistical difference between autograft (0.61±0.10) and drug-conduit (0.65±0.06). The conduit’s aligned microchannel architecture and sustained release of 4-Aminopyridine may facilitate physical guidance of axons to distal target reinnervation, while increasing nerve conduction, and in turn neurotransmitter and neurotrophic factor release. Overall, our NGC facilitates more efficient and efficacious peripheral nerve regeneration via a drug delivery system that is feasible for clinical application, with potentially transformative implications