Diffusion and relaxation contributions in the release of vitamin B6 from a moving boundary of genipin crosslinked gelatin matrices

Abstract A fundamental study was carried out to evaluate patterns of vitamin B6 release from genipin crosslinked gelatin in aqueous media at ambient temperature. Up to ninety percent crosslinking was achieved, with FTIR and WAXD data arguing for partial replacement of the triple helix with a covalent pattern of bonding between protein and crosslinker. Formation of a “composite network” yielded increasing compressive stress-at-failure values followed by a decrease as a function of genipin addition, with the yield strain decreasing continuously. Electron microscopy images showed a reduction in the size of the hydrogel pores with a higher degree of crosslinking. Experimental evidence was supported by the Flory-Rehner theory that predicted a lower swelling ratio and reduced molecular weight between adjacent crosslinks with genipin addition. Furthermore, Peppas-Sahlin equation was used to rationalise the interplay between network morphology and diffusion of bioactive compound over prolonged timeframes of release testing.