Modification of starch by graft copolymerization: A drug delivery system tested for cephalexin antibiotic

Natural polymers are defined as high value polymeric materials because of their biocompatibility with medical applications. The chemical modification of these materials by grafting synthetic polymers has received considerable attention in recent years. As the first part of this research, transmutation of the prepared carboxymethyl starch (CMS) to useful biopolymer-based materials was done by grafting acrylamide and hydroxyethylacrylate monomers using free radical polymerization. Also by chloroacetylation of starch, the graft copolymerization of the mentioned monomers via atom transfer radical polymerization was performed successfully. Both methods lead to obtain biodegradable superabsorbent copolymers. Moreover, the degree of substitution of each copolymer from both methods was determined. The prepared CMS, chloroacetylated starch, and copolymers were characterized by FTIR, DSC, thermal gravimetric analysis, XRD, and AFM, in which the latter analysis clearly shows the chain growth of the synthetic polymers on the backbone surface. Finally, in vitro drug release of cephalexin antibiotic loaded in each type of copolymers was studied in three different media (HCl solution: pH 3 and buffer solutions: pH 6.1 and pH 8).