Multi-channel chitosan-polycaprolactone conduits embedded with microspheres for controlled release of nerve growth factor

Nerve growth factor (NGF)-loaded chitosan microspheres were prepared via emulsification method using sodium tripolyphosphate as a crosslinker. Some selected chitosan microspheres were embedded into chitosan-polycaprolactone (CH-PCL) multi-channel conduits that can potentially be used for long-gap nerve repair. PCL percentages in the CH-PCLs were optimized into a region changing from around 30 to 42 wt.% while the porosity and average channel diameter of the resulting multi-channel conduits were selected as about 80% and 200 mu m, respectively. SEM images confirmed that the channels inside the conduits were longitudinally arrayed with an approximately parallel arrangement, and the NGF-loaded microspheres appeared to be embedded into the wall of channels without blocking. The compressive properties in wet state and in vitro degradation rates of CH-PCL multi-channel conduits were found to be mainly manipulated by the PCL content in the CH-PCLs whereas the cumulative amount of released NGF from the conduits could be independently regulated by altering the initial NGF load inside the embedded microspheres. The optimal microsphere-embedded CH-PCL multi-channel conduits with a dimension of around 6 mm in outer diameter and 30 mm in length were able to administrate bioactivity-preserved NGF release in a sustained and controlled manner without significant initial burst release, and the release rates of the conduits could be maintained with approximately linear characteristic over a period of time longer than 6 weeks. (c) 2012 Elsevier Ltd. All rights reserved.