Trisodium trimetaphosphate crosslinked xanthan networks: synthesis, swelling, loading and releasing behaviour

Xanthan (Xan) is a biocompatible and biodegradable polysaccharide with a promising potential as substrate for controlled drug delivery applications. Xan based hydrogels were synthesized in alkaline medium using trisodium trimetaphosphate (STMP) as crosslinking agent. Hydrogels with various crosslinking agent/polymer ratios were synthesized and subsequently characterized by the means of elemental analysis and dynamic swelling degree, model compound loading and releasing behaviour. Two physical parameters (crosslinking density and phosphate charge) are manifesting antagonistic actions by stiffening or disrupting the three-dimensional macromolecular ensemble. The highest swelling degree was obtained using an intermediate STMP:Xan ratio in which case the opposing effects of the two forces are well balanced. The synthesized networks are pH sensitive. In acid and alkaline media the swelling degrees are lower by comparison to neutral pH. The entrapping and releasing behaviour of the newly synthesized xanthan networks were studied using methylene blue as a cationic model molecule. The releasing kinetics present a first-order model.