Molecular characterisation of hot moulded alginate gels as a delivery vehicle for the release of entrapped caffeine

This work explores the process of alginate molecule crosslinking to form cohesive gels that were induced by the addition of calcium ions at various stoichiometric equivalents. Polysaccharide gels were used as a delivery vehicle for the study of transport phenomena of entrapped caffeine as the bioactive compound. Initial physicochemical characterisation through FTIR and WAXD of the alginate matrix showed successful inclusion of caffeine in the bulk system. Rheological analysis in the form of dynamic oscillation in-shear highlighted issues of developing network integrity and its eventual collapse with increasing levels of the crosslinker. Swelling in neutral solvent (water molecules) yielded information on the molecular features of the gel, as determined by the Flory-Rehner theoretical framework. Analysis of molecular transport with modified Fickian diffusion equations showed anomalous behaviour and a sustained release of caffeine. Overall, alteration in mesh size and diffusion parameters can be ascribed to the microstructural changes controlled by calcium crosslinking and the formation of junction zones in the alginate network.