An innovative hyaluronic acid product for viscosupplementation in patients with osteoarthritis

      Purpose: The specific formulation [HA+sorbitol] of Synolis™ V-A is based on a high molecular weight of HA (> 2 MDa in the final sterilized gel) from non animal origin, with a high HA concentration (20 mg/ml), combined with a high concentration of a free radical scavenger, the sorbitol (40 mg/ml). The aims of this study are to evaluate the mechanical/rheological properties and the resistance to free radicals degradation of Synolis™ V-A.
      Methods: The rheological properties are analyzed by frequency sweep experiments at 25°C thanks to a parallel plate rheometer (AR2000, TA Instruments). The resistance to free radical degradation is observed visually by adding an oxidant agent (H2O2) on the viscosupplement (Weight of H2O2 = 1/15 x Weight of viscosupplement), by heating the mixing at 60°C and by watching the flow of the product over time. The resistance to free radical degradation is also followed thanks to an AR2000 rheometer (time sweep experiments at 37°C). Results of resistance to degradation obtained with Synolis V-A are compared to 5 other commercial viscosupplements.
      Results: Visco-elastic properties of Synolis V-A. Synolis V-A is characterized by a visco-elastic behavior close to the human synovial fluid (viscous and elastic moduli crossing at 0.4 Hz) and high viscous and elastic moduli due to the high affinity between HA and sorbitol that stabilizes the structure through a very dense network of hydrogen bonds. Resistance to free radical degradation. In presence of free radicals (H2O2), Synolis V-A demonstrates a much higher resistance against free radicals than the other commercial viscosupplements as shown by the visual observation and by the rheological properties.
      Conclusions: Synolis V-A is an innovative viscosupplement made of hyaluronic acid and sorbitol. Due to its patented formulation and manufacturing process, Synolis V-A has outstanding rheological properties and a high resistance against in vivo degradation in the joint. As demonstrated by several experiments, Synolis V-A is characterized by a visco-elastic behaviour close to the human synovial fluid, a very high elasticity and viscosity and a high resistance to free radical degradation. The synergetic combination of HA of high molecular weight and sorbitol, combined with a specific manufacturing process which included a final moist heat sterilization, allows to obtain unique properties. Moreover, due to the high affinity between HA and sorbitol, Synolis V-A is stabilized through a very dense network of hydrogen bonds. This complex structure of gel presents remarkably high visco-elastic properties. Consequently, thanks to these particular visco-elastic properties, Synolis V-A has a high ability to lubricate joints and to absorb shocks, as with a healthy synovial fluid. On the other hand, the high ability of sorbitol to scavenge and neutralize free radicals (= antioxidant effect) allows to limit the degradation of the gel in order to increase the half-life of the product in the joint (as described in the literature, free radical degradation is an important factor of HA degradation in the joint and is a key factor of the OA (free radicals is associated with chondrocyte death and cartilage destruction).