Kinetics of long-term degradation of different molar mass hyaluronan solutions studied by SEC-MALLS

The degradation of hyaluronan of four molecular weights in aqueous solutions containing sodium azide as a protectant was studied by SEC-MALLS determination of molecular mass and polydispersity and conformation parameters. The solutions were stored either at laboratory or refrigerator temperatures for up to seven months. After this time the molar mass decreased in 9-15% (room temperature) or 5-10% (fridge) depending also on the storage conditions of solid samples from which the solutions were prepared. Two degradation phases were observed at room temperature conditions. Two kinetic models were employed to fit the data - zero order and exponential with no statistical preferences of any of them. The polydispersity of all samples was low and remained unaltered during the whole degradation at both temperatures which indicates non-random mechanism of degradation.