Release Properties of Hydrogels: Water Evaporation from Alginate Gel Beads

Abstract

Encapsulation in alginate hydrogels has been extensively used for several applications in food, pharmaceutical, and biomedical fields. The rational design of a functional polymer network is based on the identification of key parameters and mechanisms governing rate and extent of release of the immobilized molecular species. In the present work, a calorimetric study of the water evaporation under non-isothermal conditions is aimed at evaluating functional properties of a series of alginate-based gel beads. The experiments show how a number of variables, such as scan rate, calcium and alginate concentration, operational procedures, and addition of biopolymer co-solutes influence the temperature evolution of the water evaporation from beads. Given the simplicity and the rapidity of the calorimetric experiment, the issue is raised that a scaling approach could be reached by using water as reference material for the prediction of the diffusion kinetics of encapsulated molecules of variable size and properties.

In-vitro digestion of different forms of bovine lactoferrin encapsulated in alginate micro-gel particles

“…Kim (1990) has shown that the use of higher calcium ion concentration during cross-linking of alginate causes a rapid shrinking of the alginate gel leading to formation of water cavities within the gelled layer of the particles due to rapid release of bound water from the alginate network. In agreement with this, studies have shown that the formation of a compact gel results when using high calcium ion concentrations and this is associated with possible collapse of some junction zones leading to increased pore sizes (Donati & Paoletti, 2009) and formation of inhomogeneous gel structure which can affect the permeability (Skjåk-Braek, Grasdalen, & Smidsrød, 1989;Bellich, Borgogna, Cok, & Ces aro, 2011). This ultimately will cause greater diffusion of Lf during micro-gel particle formation.…”

Programmed Platelet-Derived Growth Factor-BB and Bone Morphogenetic Protein-2 Delivery from a Hybrid Calcium Phosphate/Alginate Scaffold

“…This hypothesis is consistent with known release behaviors of alginate hydrogels in the literature, with a greater amount of crosslinking generally serving to slow protein release from the hydrogel. 36,39 Similarly, when a 3% alginate hydrogel was applied as a coating to ReCaPP scaffolding, linear release was observed over the first 6 days, at a slower rate of release compared with 1% alginate hydrogels. This difference can be explained by the concentration of alginate used in the hydrogels; as the percentage of alginate increases, total release is correspondingly extended.…”

Isothermal dehydration of thin films

“…The data here presented give further strength to these basic concepts, although clear limitations and corrections to this approach arise when the isothermal dehydration occurs at high temperature. Therefore, a straightforward use of the same formalism in the investigation of water dehydration in the scanning mode is not possible at this stage, although the scanning curves of aqueous polymer solutions and polymer gels previously published [25,26] effectively follow the trend of the HF curves as a function of temperature, as reported in Fig. 6c.…”