(513e) Multifunctional Scaffold for Intervertebral Disc Regeneration

Lower back pain is one of the most common medical problems in the world. One of the main causes of lower back pain stems from damage or dehydration of the nucleus pulposus, as a result of degenerative disc disease. These biological changes reduce the hydrostatic pressure on the internal surface of the annulus fibrosis, causing abnormal compressive stress on the intervertebral disc with physiological loading. After repeated loads, this can lead to tears, cracks and fissures in the annular tissues. Back pain can develop as a result of nucleus tissue migrating through the annulus and impinging on nerve roots. Currently, the major surgical treatments for degenerative disc disease include discectomy, spinal fusion and total disc arthroplasty; however, total nucleus pulposus replacement is also being investigated. These treatments target pain control rather than repair of the native tissue. Recently, research has focused on using cell-based therapy to increase the viable cell population in the disc and increase production of extracellular matrix components. Within these cell-based tissue engineering strategies, several biomaterials have been investigated as three-dimensional matrices, including polylactic acid (PLA) and poly(lactic-co-glycolic-acid) (PLGA). However, these matrices have limited control over pore interconnectivity, mechanical properties and degradation rates. These scaffolds also lack biological components which aid in improving the biocompatibility of synthetic materials. The primary goal of this work is to synthesize a multifunctional tissue engineering scaffold for the regeneration of intervertebral disc tissue. In this study, the swelling, degradation, and mechanical properties of three-dimensional hydrated copolymer networks comprised of poly(N-isopropylacrylamide) and natural chondroitin sulfate A are investigated. PNIPAAm is hydrophilic at room temperature, but above 32°C the chains become hydrophobic and entangle to form physical crosslinks, resulting in a gel. In this work, monomer NIPAAm is co-polymerized with methacrylated chondroitin sulfate A to increase the water content, elasticity, and biocompatibility of PNIPAAm hydrogels. In future work, the potential of these injectable polymers to serve as carriers for mesenchymal stem cells and therapeutic proteins will be investigated.