Sustained release of neurotrophin-3 and chondroitinase ABC from electrospun collagen nanofiber scaffold for spinal cord injury repair

Nerve regeneration after spinal cord injuries (SCI) remains suboptimal despite recent advances in the field. One major hurdle is the rapid clearance of drugs from the injury site, which greatly limits therapeutic outcomes. Nanofiber scaffolds represent a potential class of materials for enhancing nerve regeneration because of its biomimicking architecture. In this study, we investigated the feasibility of incorporating neurotrophin-3 (NT-3) and chondroitinase ABC (ChABC) onto electrospun collagen nanofibers for SCI treatment. By using microbial transglutaminase (mTG) mediated crosslinking, proteins were loaded onto electrospun collagen nanofibers at an efficiency of similar to 45-48%. By combining NT-3 with heparin during the protein incorporation process, a sustained release of NT-3 was obtained (similar to 96% by day 28). As indicated by dorsal root ganglion outgrowth assay, NT-3 incorporated collagen scaffolds supported neuronal culture and neurite outgrowth for a longer time period than bolus delivery of NT-3. The presence of heparin also protected ChABC from degradation. Specifically, as evaluated by dimethylmethylene blue assay, bioactive ChABC was detected from collagen scaffolds for at least 32 days in vitro in the presence of heparin (similar to 32% of bioactivity retained). In contrast, ChABC bioactivity was only similar to 1.9% by day 22 in the absence of heparin. Taken together, these results clearly demonstrated the feasibility of incorporating NT-3 and ChABC via mTG immobilization to produce protein-incorporated collagen nanofibers. Such biofunctional nanofiber constructs may find useful applications in SCI treatment by providing topographical signals and multiple biochemical cues that can promote nerve regeneration while antagonizing axonal growth inhibition for CNS regeneration. (C) 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 100A: 236-242, 2012.