Poly(ethylene glycol)–carboxymethyl chitosan-based pH-responsive hydrogels: photo-induced synthesis, characterization, swelling, and in vitro evaluation as potential drug carriers Original Research Article

In this study, carboxymethyl chitosan was prepared, characterized, and then photo-induced graft copolymerized with poly(ethylene glycol) under a nitrogen atmosphere in aqueous solution using 2,2-dimethoxy-2-phenyl acetophenone (DMPA) as the photo-initiator. The grafting copolymerization process was confirmed and the resulting copolymers were characterized using differential scanning calorimetry (DSC), FTIR spectroscopy, 2D-X ray diffraction, and elemental analysis. The kinetics of the grafting reactions was also studied. Under the applied experimental conditions, the optimum grafting values were obtained at: CMCs = 0.2 g, PEGA = 249 mM, DMPA = 10.4 mM at a 2 h reaction time. Some of the resulting copolymers were selected and used in the presence of methylene bisacrylamide (MBA) as a crosslinking agent to develop pH-responsive hydrogel matrices. The swelling characteristics and the in vitro release profiles of 5-fluorouracil (5-FU), as a model drug, from the hydrogels were investigated. The results revealed that the hydrogel matrices developed in this study can be customized to act as good candidates in drug delivery systems.