The behaviour of hyaluronan solutions in the presence of Hofmeister ions: A light scattering, viscometry and surface tension study

Abstract

Dynamic light scattering (DLS), viscosity and surface tension (SFT) measurements were used to characterize influence of salts containing ions of Hofmeister series (Na₂SO₄, (NH₄)₂SO₄, NaSCN, NH₄SCN and NaCl) on the behaviour of hyaluronan in diluted solutions at a temperature range of 15-45 °C. The results of the study showed that chaotropic and kosmotropic ions notably influenced the folding and unfolding of hyaluronan coils due to interactions between a respective ion and hydrophilic or hydrophobic patches present in the backbone of the polymer chains. This was mainly proved by viscosity and light scattering measurements. The temperature dependence of the hydrodynamic diameter of the hyaluronan coil determined by DLS demonstrated that combinations of chaotropic and kosmotropic ions in one salt (NaCl, NaSCN and (HN₄)₂SO₄) can stabilize the size of the coil in a wide range of temperatures. Tensiometry measurements indicated that certain types of ions present in the solution caused an unfolding of the hyaluronan coils, leading to a decrease of SFT.