Physicochemical study of modified dextrans with a β-cyclodextrin polymer

摘要

The aim of this work was the design of a pH-sensitive system consisting of an amphiphilic polymer and a β-cyclodextrin coepichlorhydrin water-soluble polymer (pCD/EP). Different modified dextrans were synthesized from reaction of dextran (Mw=40,000) with phthalic anhydride, 2-phenylglutaric anhydride and 1,2-cyclohexane dicarboxylic anhydride with grafting ratio around 2%. The viscometric study of modified dextrans with pendant cyclohexane carboxylic acid groups mixed with pCD/EP was performed at pH 1 and 7 and showed a small increase of reduced viscosity compared to mixtures of dextran and pCD/EP. The phase diagram shows association phase-separation at low pH, whereas monophasic mixtures were obtained at pH higher than the pKa. Furthermore this phase-separation is reversible according to the pH. The use of 8-anilinonaphtalene-1-sulfonic acid, as a fluorescent probe, allowed us to determine the inclusion constants of the modified dextrans. Complexation constants higher by 1 order of magnitude for the most hydrophobically modified dextrans were obtained at pH 2.5 compared to pH 7.