Shear-Rate Dependence of the Intrinsic Viscosity of Sodium Hyaluronate in 0.2 M Sodium Chloride Solution

Abstract

The dependence of the intrinsic viscosities ([η]) of seven well-characterized sodium hyaluronate (HA) samples in 0.2 M NaCl solution on shear rates was investigated using four kinds of viscometers with γ values ranging from 0.1 to 2000 s-1. Molecular weight distributions of these samples were checked by a gel permeation chromatograph connected to a low-angle laser light scattering photometer. The determination of [η] at zero shear rate ([η]0) for high molecular weight HA had to be made using low shear viscometers with < 250 s-1, since [η] showed remarkable shear thinning behavior with increasing molecular weight. Double logarithmic plots of [η]0vs. Mw (the weight-average molecular weight) for HA in 0.2 M NaCl solution gave a relation expressed by for where [η]0 was written in dl/g unit. The shear thinning behavior of [η] of HA in the solvent was analyzed by the Rouse-Zimm bead-spring model proposed by Fixman. Consequently, the-dependence of HA in 0.2 M NaCl solution could be well described by this model of large viscosity expansion factors, and suggested that an HA chain in the solvent is a fairly expanded random coil by excluded volume effects. © 1994, The Pharmaceutical Society of Japan. All rights reserved.