Modification of dextran using click-chemistry approach in aqueous media

In this paper, dextran was modified using click-chemistry. Each reaction step was done under aqueous conditions, including the introduction of azide functionalities to the backbone of the polysaccharide. The reaction consisted of the synthesis of 1-azido-2,3-epoxypropane, which was etherified onto the backbone of the polysaccharide using base-catalysis in water/isopropanol mixture at ambient temperature. The achieved degree of substitution (DS) of azide groups in dextran was up to 0.20. Alkyne-end-functionalized poly(ethylene glycol) monomethyl ether (PEG-MME) was then grafted onto the synthesized azide-functionalized dextran having a DS of 0.08 or 0.16 by copper-catalyzed azide–alkyne cycloaddition (CuAAC). In the case of the lower DS valued dextran, a quantitative reaction of the azides was achieved within an hour, whereas the CuAAC-reaction of dextran having DS = 0.16 yielded a DS = 0.10 of grafted poly(ethylene glycol). Prolonging the reaction time to 24 h did not further improve the conversion of azides, which may be due to steric factors.