3D printed nerve guidance conduit for biologics‐free nerve regeneration and vascular integration

Abstract There is a clinical need for an effective nerve guidance conduit to treat peripheral nerve injuries. Many studies have explored different materials and active cues to guide neural regeneration, with some success. However, none have demonstrated a comparable or better functional recovery than the clinical standard autograft. Autografts are often insufficient for reconstruction of an injury to long nerves such as the sciatic or brachial plexus. Synthetic nerve guidance conduits (NGCs) have been investigated for these injuries to guide axonal regeneration and lead to functional recovery. We have designed a biologics-free hydrogel-based multi-channel conduit with defined microscale features to guide axonal outgrowth. To investigate extraneural vascular infiltration and its effects on functional recovery, we also designed a multi-microchannel conduit with defined regularly spaced micropores, orthogonal to the axon guidance channels. Using our custom-built Rapid Projection, Image-guided, Dynamic (RaPID) bioprinting system, we are able to fabricate each hydrogel conduit within minutes from a milliliter-volume prepolymer vat. With our state-of-the-art printing platform, we have achieved NGCs with a consistent channel wall width of 10 microns. We implanted the NGCs for 17 weeks in a murine sciatic nerve transection injury model. We assessed the functional recovery by dynamic gait analysis throughout the recovery period and by compound muscle action potential (CMAP) electrophysiology before NGC harvesting. Both the non-porous and micro-porous conduit groups led to functional nerve regeneration on par with the autograft group. Further, both conduit groups resulted in restoration of bulk motor function to pre-injury performance. Translational Impact Statement We have developed a synthetic therapeutic that can be implanted to aid nerve regeneration after a debilitating injury that performs similarly to the current clinical standard treatment. One major hurdle to clinically translating an implantable therapeutic is needing to include biologics such as cells or active biomolecules, which increases the regulatory burden. With this in mind, we systematically developed a biologics-free synthetic hydrogel nerve guidance conduit, composed of polymer backbones that have been used in many FDA-approved applications, capable of restoring motor function.