Regioselective synthesis and biological activity of oxidized chitosan derivatives

Oxidized chitosan derivatives with various degrees of oxidation (DS, 0.1-1.0) were prepared by the treatment of chitosan with CrO3/aq HClO4 or by the oxidation of 3-O- and N-protected chitosan with 30% aq H2O2/Na2WO4 followed by 3-O- and N-deprotection. The oxidized products were then N-acetylated with Ac2O in order to improve their water-solubility. Although the oxidized chitosan derivative of DS 0.28 and the degree of N-acetylation of chitosan (DA) 38% was insoluble in the pH 3-8 region, that of DS 0.26 and DA 76% was soluble in the neutral pH range. The newly-prepared acetylated and oxidized chitosan derivatives were found to suppress the chemiluminescence response of inflammatory cells such as canine polymorphonuclear cells (PMNs). Analysis by the surface plasmon resonance method revealed that the bind and release behavior of PMNs to acetylated oxidized chitosan derivatives was similar to that against carboxymethylated chitosan derivatives. The amount of water-soluble chitosan derivative bound to cytokine IL-8 was found to be affected by the structural and electronic features of the chitosan substituents in the chitosan chain. Copyright (C)2003 John Wiley Sons, Ltd.