Biomimetic construction of a lubricious hydrogel with robust mechanics via polymer chains interpenetration and entanglement for TMJ disc replacement

Developing a temporomandibular joint (TMJ) disc substitute with reliable long-term functional support has faced a huge challenge in replicating the unique microarchitecture, biomechanics and lubrication of the natural tissue. Herein, a novel biomimetic hydrogel consisting of graphene oxide nanosheets modified anionic polyurethane (nGO-APU) and polyvinyl alcohol (PVA) was successfully fabricated through combined freeze-thawing and annealing treatment. Of which, the annealed PVA (a-PVA) with entanglement network acted as the main frame to provide mechanical support, while the interpenetrated nGO-APU chains endowed the function for water retention and lubrication, thus resisting the compressive loads and fulfilling a durable energy absorbing and cushion. The resultant nGO-APU/a-PVA hydrogel achieved better lubrication effect through the synergistic effect of fluid film and boundary lubrication, exhibiting a low friction coefficient of about 0.06, close to the natural TMJ disc. After implantation into rabbit TMJ for up to 24 weeks, the nGO-APU/a-PVA hydrogel kept the structural stability to offer effective protection against wearing of the cartilage, meanwhile ameliorating the worsening of osteoarthritis. The finite element analysis (FEA) further proved that the resultant hydrogel could effectively disperse the applied stress and dissipate energy under practical loading conditions. This strategy based on a biomimetic hydrogel with enhanced mechanical stability and lubrication performance shows clinical promise for TMJ disc replacement.