Comparative properties of hyaluronan and chitosan in aqueous environment

In this paper, our objective is to compare the physico-chemical properties of chitosan (CHIT) and hyaluronic acid (HA), two important polysaccharides often used in biomedical or cosmetic applications. Polymer-polymer interactions as well as polymer-solvent interactions, studied by experiments and by molecular modeling, are discussed for the two biopolymers in presence of aqueous environments. HA and CHIT have similar non-freezing water content, although HA retains more water than CHIT at large degree of relative humidity (RH). Thermal degradation is larger for HA. The specific viscosity at zero shear rate of CHIT deviates from the master curve, whereas that of HA superimposed nicely. The solution viscosity of concentrated solutions of CHIT continuously decreases in the shear rate range between 0.5 up to 100 s^?1, whereas HA shows a Newtonian plateau at low shear rates. Dynamic rheology of semi-diluted solutions of HA shows storage modulus G?? lower than the loss modulus G?? up to 30 g/L but that of CHIT at 20 g/L shows G?? > G?? at nearly the same overlap parameter. The viscosity of CHIT solution is less influenced by temperature than that of HA. These results clearly underline the importance of interchain interactions for CHIT in a good solvent. Molecular modelling is used to provide insights on both the aggregated state and solution state of the two polysaccharides. Interchain interactions in the organized models were predicted larger for CHIT than for HA whereas the interaction between the polysaccharide and the solvent molecules are larger for HA than for CHIT. This approach rationalizes the experimental observations: the higher solvation of HA and the higher ability to aggregate for CHIT.