Microstructure and in vivo characterization of multi-channel nerve guidance scaffolds

In a previous study, we demonstrated a novel manufacturing approach to fabricate multi-channel scaffolds (MCS) for use in spinal cord injuries (SCI). In the present study, we extended similar materials processing technology to fabricate significantly longer (5X) porous poly caprolactone (PCL) MCS and evaluated their efficacy in 1 cm sciatic peripheral nerve injury (PNI) model. Due to the increase in MCS dimensions and the challenges that may arise in a longer nerve gap model, microstructural characterization involved MCS wall permeability to assess nutrient flow, topography, and microstructural uniformity to evaluate the potential for homogeneous linear axon guidance. It was determined that the wall permeability dramatically varied from 0.02 +/- 0.01 x 10(-13) to 21.7 +/- 11.4 x 10(-13) m(2) for 50% and 70% porous PCL, respectively. Using interferometry, the porous PCL surface roughness was determined to be 10.7 +/- 1.2 mu m, which is believed to be sufficient to promote cell integration. Using micro computed tomography, the 3D MCS microstructure was determined to be uniform over 1 cm with an open lumen volume of 44.6% +/- 3.6%. In vivo implantation, in the rat sciatic nerve model, over 4 weeks, demonstrated that MCS scaffolds maintained structural integrity, were biocompatible, and supported linear axon guidance and distal end egress over 1 cm. Taken together, this study demonstrated that MCS technology previously developed for the SCI is also relevant to longer nerve gap PNI.