Novel modified starch–xanthan gum hydrogels for controlled drug delivery: Synthesis and characterization

This work was intended to develop a new cross-linked gelatinized starch–xanthan gum hydrogel system, to characterize the properties of the new material, and to explore its potential applications in controlled drug delivery. Cross-linked starch–xanthan gum polymers were synthesized with varying levels of xanthan gum and sodium trimetaphosphate (STMP). The reaction of starch–xanthan gum polymers with STMP was examined using solid 31P NMR spectroscopy and FTIR. Morphology of the films made from the new polymers was studied by scanning electron microscopy. The swelling properties and the network parameters such as gel mesh size of the films were investigated. The permeation of solutes with various molecular weights and charges across the films was determined. 31P NMR and FTIR spectra showed that both starch and xanthan gum were reacted with STMP. The swelling ratio of the films was higher at higher STMP and xanthan gum levels. The gel mesh size increased with increasing swelling ratio varying from 2.84 to 6.74 nm. Permeability of anionic drugs across the polymeric films was significantly lower than their neutral form due mainly to the electrostatic repulsion between the negatively charged drugs and the polymer. The results suggest that the new cross-linked starch–xanthan gum hydrogels can be potentially used as a film-forming material in controlled release formulations.