Effects of sodium chloride, guanidine hydrochloride, and sucrose on the viscoelastic properties of sodium hyaluronate solutions

Effects of sodium chloride (NaCl), guanidine hydrochloride (GuHCl), or sucr ose on the viscoelasticity of sodium hyaluronate (NaHA) solutions were stud ied. NaCl and GuHCl decreased both storage and loss moduli, while sucrose i ncreased both moduli. The critical concentration C* was determined as an in flection point in the plot of zero shear specific viscosity vs concentratio n for NaHA solutions with and without NaCl, GuHCl, or sucrose. It is sugges ted that sodium ions or guanidinium ions shield the electrostatic repulsion of NaHA molecules, hence reduce the coil dimension, and CX shifted to high er concentrations. However, sucrose enhances the entanglement coupling betw een NaHA molecules and retards the disentanglement of molecular chains or p romotes to create hydrogen bonds, and then C* for NaHA solutions with sucro se shifts to lower concentrations. This is in agreement with the results of light scattering measurements in the presence of 0.2M NaCl. Both the radiu s of gyration and hydrodynamic radius of NaHA were reduced in dilute soluti ons by the addition of sucrose, and added sucrose enhances the interaction between NaHA monomer units. In the case of concentrated NaHA solution, such interactions result to increase the storage and lass moduli because of the enhancement of temporary network formation. (C) 1999 John Wiley & Sons, In c.