Synthesis and characterization of pH-responsive hydrogels based on chemically modified Arabic gum polysaccharide

This work describes the preparation of a pH-responsive hydrogel from Arabic gum (AG) chemically modified with glycidyl methacrylate (GMA). This report first describes the chemical modification of AG and next the synthesis and characterization of the hydrogel obtained. An appropriate mixture of water and DMSO was used to dissolve AG and GMA. The presence of GMA groups in the modified structure of Arabic gum (AG-MA) was detected by 13C NMR, 1H NMR, and FT-IR techniques. The cross-linking reaction of AG-MA leads to formation of an AG-MA hydrogel, which was characterized by solid-state 13C-CP/MAS NMR and FT-IR spectroscopy. Morphology was visualized by scanning electron microscopy. It was observed in water uptake tests that AG-MA hydrogels showed significant pH dependence, which affected the water absorption transport mechanism. In the studied pH range, it was found that the transport mechanism of water into AG-MA hydrogel was controlled by Fickian diffusion and polymer relaxation (anomalous transport). At high pH values, the water transport profile became more dependent on polymer relaxation. This effect was attributed to the increase in the ionized groups of glucuronic acid segments, which contributed to electrostatic repulsion among the groups and led the gel polymer network to expand. AG-MA hydrogels exhibited pH-responsive, demonstrating them to be appropriate materials for further tests as drug carriers.