Azide-functionalization of melanin free pullulan for further use in click chemistry

Full text: Pullulan is a hydrophilic polysaccharide, with low toxicity, great biodegradability and biocompatibility, possible to be used in drug/gene delivery systems. In order to produce a polysaccharide with specific properties, different chemical modifications may be done in pullulan, among then there are the chemical reactions of etherification, oxidation, nucleophilic displacement and grafting. This paper describes the preparation of the melanin free pullulan modified with azides groups in the polymer backbone. The product of the modification will be used in further 'click chemistry' reactions to graft polymerization with alkyneend group hydrophobic homopolymers in order to produce amphiphilic structures. Thereafter, the resulted copolymers will be applied on drug delivery system due to its aggregation capability in aqueous solutions. To obtain the azide functionalized pullulan, a compound with azide group and brome, 2-azidoethyl 2- bromopropanoate, was synthesized in two steps: firstly, the intermediated 2- azidoethanol (AE) was obtained by reacting 2-bromoethanol with sodium azide and then it was reacted with 2-bromopriprionyl bromide, in the presence of triethylamine to produce AEBP. At last, the compound synthesized were used in the pullulan functionalization, in the presence of potassium carbonate. Part of the hydroxyl groups from pullulan were reacted with the halide from the AEBP. The chemical structure of the AE, AEBP and modified pullulan were confirmed by ¹H NMR and FTIR. Besides that, the complementary techniques of contact angle, UV/Vis and CHN elemental analysis were also used to confirm the modification on pullulan structure. (author)