Design and synthesis of three-dimensional hydrogel scaffolds for intervertebral disc repair

Intervertebral disc degeneration is a major cause of low back pain, which affects a large proportion of the population. Spinal fusion is one of the common solutions to restrict motion and stabilize, however biomechanical changes cause further problems. Although tissue engineered IVD structures and cell based therapies are being developed it is crucial that the structures are able to support spinal load. In this paper we report a biomaterial based regenerative approach with the first stage being the synthesis and characterisation of a group of hydrogels that has the potential to be further developed for cell-biomaterial based approaches. Copolymers of 2-hydroxyethylmethacrylate and a multifunctional comonomer, pyromellitic glycerol dimethacrylate p(HEMA/PMGDM) were synthesized and the effects of composition on the thermal behaviour and dynamic mechanical behaviour of these copolymeric hydrogels and the feasibility of use as biomaterials for IVD are reported. The HEMA-co-PMGDM copolymeric networks were shown to have highly controllable viscoelastic properties; the presence of a strong beta transition in the glassy region (in vivo temperature range) and the energy absorption and dissipation of the system (critical to disc function) could be easily controlled by tailoring the copolymer composition, crosslinking agent concentration and polymerisation methods, which is of great significance for the end use of these materials, as the essential function of the gelatinous nucleus is to resist, dampen and redistribute mechanical forces within the spine outwards towards the constricting annulus. To date there is no previous research incorporating PMGDM into hydrogel systems for biomedical applications.