Incorporation of Chitosan Microspheres into Collagen-Chitosan Scaffolds for the Controlled Release of Nerve Growth Factor

BACKGROUND Artifical nerve scaffold can be used as a promising alternative to autologous nerve grafts to enhance the repair of peripheral nerve defects. However, current nerve scaffolds lack efficient microstructure and neurotrophic support. METHODS Microsphere-Scaffold composite was developed by incorporating chitosan microspheres loaded with nerve growth factor (NGF-CMSs) into collagen-chitosan scaffolds (CCH) with longitudinally oriented microchannels (NGF-CMSs/CCH). The morphological characterizations, in vitro release kinetics study, neurite outgrowth assay, and bioactivity assay were evaluated. After that, a 15-mm-long sciatic nerve gap in rats was bridged by the NGF-CMSs/CCH, CCH physically absorbed NGF (NGF/CCH), CCH or nerve autograft. 16 weeks after implantation, electrophysiology, fluoro-gold retrograde tracing, and nerve morphometry were performed. RESULTS The NGF-CMSs were evenly distributed throughout the longitudinally oriented microchannels of the scaffold. The NGF-CMSs/CCH was capable of sustained release of bioactive NGF within 28 days as compared with others in vitro. In vivo animal study demonstrated that the outcomes of NGF-CMSs/CCH were better than those of NGF/CCH or CCH. CONCLUSION Our findings suggest that incorporation of NGF-CMSs into the CCH may be a promising tool in the repair of peripheral nerve defects.