Diffusion kinetics of vitamin B6 from phase-separated gelatin and agarose gels using blending law modelling

Abstract

This study was conducted to understand the diffusion kinetics of vitamin B6 from composite gels of gelatin and agarose via blending law and diffusion modelling. Fourier-transform infrared spectroscopy (FTIR), X-ray Diffraction (XRD), confocal laser scanning microscopy (CLSM) and small-deformation dynamic oscillation in shear were used to analyse the structural properties of the composite gels. UV–vis spectroscopy was employed to study the diffusion kinetics of vitamin B6 from the gelatin-agarose gels. FTIR confirmed the absence of chemical interactions between gelatin and agarose in the mixture. XRD demonstrated that vitamin B6 was thoroughly hydrated in the polymeric mixture that balanced disordered polymer segments with structured junction zones. CLSM provided tangible evidence of the phase-separated nature of the two macromolecules, and blending law predicted the phase volume and their effective concentrations in the system. The diffusion of vitamin B6 from composite gels, prepared with estimated phase volumes and effective concentrations of the individual components according to rheological blending law, was measured with UV–vis spectroscopy. As far as we are aware, for the first time, rheological blending law was recast to provide the corresponding blending law for diffusion. Thus, theoretical diffusion coefficients were calculated and compared favourably with those from the experimental studies. Results argue for the presence of a blending law-based diffusion theory that can predict the diffusion kinetics of bioactive compounds in aqueous composite gels.