Controlled release of ascorbic acid from genipin-crosslinked gelatin matrices under moving boundary conditions

The purpose of this research is to investigate swellable genipin-crosslinked gelatin matrices for the controlled delivery of water soluble vitamins (ascorbic acid). The following methods were utilized to describe the physicochemical properties of the system: micro differential scanning calorimetry and small deformation dynamic oscillation in shear. Hydrogel microstructural properties were reported in terms of the average molecular weight between crosslinks and network mesh size. Degree of crosslinking in gels with concentration of genipin crosslinker from 0 to 2.8% (w/w) was measured using ninhydrin assay and UV-vis spectroscopy. Swelling of the gel matrix in aqueous solvent was followed and colorimetric methods were used to measure the diffusion kinetics of ascorbic acid from the gel to the surrounding aqueous phase. Results after treatment of swelling data with improved Fickian theory found matrix swelling was limited by the relaxation of polymer chains. Significance of results lies in the derivation of apparent diffusion coefficients for the transport of water molecules and bioactive compound at 85% and 98% crosslinking that relates the kinetics of bioactive compound release to mesh size of the polymeric network. Thus, there is strong evidence that modulation of the extent of crosslinking impacts on hydrogel morphological characteristics and structural properties, with resulting control of bioactive compound release. Outcomes may be implemented in targeted delivery of bioactive compounds, including vitamins, within the human body, for improved bioavailability.