Regenerating spinal disc tissue using a vinyl-lysine urethane scaffold

The focus of this work was to fabricate a biodegradable urethane-based scaffold and assess its suitability for annulus fibrosus (AF) regeneration. A vinyl-lysine urethane (VLU) scaffold (pore sizes between 30 and 250 mum; porosity = 70.0+/-5.0%) was synthesized by reacting a lysine-based polycarbonate divinyl oligomer with acrylate monomers in the presence of sodium bicarbonate salt crystals. A millipore filter cytotoxicity test, in conjunction with high performance liquid chromatography, was used to assess aspects of biocompatibility and indicated that the salt extraction process removed toxic unreacted acrylate monomers that were entrapped within the polymer matrix. In vitro biodegradation studies using cholesterol esterase to model in vivo macrophage hydrolytic activity showed that VLU scaffolds degraded 15.43+/-0.34% over a 4-week period. Bovine AF cells, maintained in three-dimensional culture, attached to VLU scaffolds and formed tissue containing glycosaminoglycans and collagen. These findings demonstrate the potential of using synthetic urethane-based scaffolds for AF regeneration.