Effect of new hydrophobic modification of hyaluronan on its solution properties: evaluation of self-aggregation

Solution properties of novel hyaluronan (HA) derivatives were investigated and their self-aggregation evaluated for drug delivery purposes. The HA had been grafted by C-8 and C-12 chains onto -OH groups Of D-glucuronic acid via carbamate bond at low and high degrees of substitution (DS), so that the carboxyl groups of the polysaccharide were preserved. Surface tension, theological, and viscosity properties were studied. All the derivatives displayed surface-activity by means of a decrease of surface tension (gamma) of their solutions, and a breakpoint on gamma-logC dependence suggests an aggregates formation. The high-molecular derivatives of high DS exhibited the most efficient surface activity and shear-thinning rheological behavior comparing to the shorter derivatives of low DS. The similar Mark-Houwink-Sakurada plot coefficient, (alpha) over bar = 1.06, for both the native and modified HA manifests that the modification did not meaningfully alter the stiffness of the HA chains. (C) 2008 Elsevier Ltd. All rights reserved.