Self-complex formation of nicotinamide-modified dextran with carboxymethyldextran using their degradation products

A pseudo-metabolic cycle as a self-degradation system was designed: enzymat ic degradation products from a polysaccharide generate oxidants which intro duce a cationic charge into the polysaccharide chains, and can form a polyi on complex with an anionic polysaccharide. As a component of such a system, dextran, with various degrees of nicotinamide substitution, was prepared. Its degradation by dextranase, redox reaction via glucose oxidase-catalysis , and polyion complex formation with carboxymetyl dextran (CMD) were examin ed. Nicotinamide-modified dextran (NA-Dex) with nine nicotinamide moieties per 100 glucose units was soluble in PBS and completely oxidized by >100 mM H2O2 The oxidized type of NA-Dex was found to form a 1 : 1 complex with CM D. By the addition of dextranase, isomaltase, and glucose oxidase (GOD) to phosphate buffer solution of the reduced type of NA-Dex and CMD, the transm ittance of the solution dropped, suggesting polyion complex formation via t he oxidation of 1,4-dihydronicotinamide in NA-Dex by H2O2 generated from GO D-catalytic reaction. These findings are of great importance for designing a self-complex formation system aimed at biodegradable and osillative drug release.