Abstract
The interest toward alginate and nanoemulsion-based hydrogels is driven by the wide potential of application. These systems have been noticed in several areas, ranging from pharmaceutical, medical, coating, and food industries. In this investigation, hydrogels prepared through in situ calcium ion release, starting from lemongrass essential oil nanodispersions stabilized in alginate aqueous suspensions in the presence of the nonionic surfactant Tween 80, were evaluated. The hydrogels prepared at different concentrations of oil, alginate, and calcium were characterized through rheological tests. Flow curves demonstrate that the hydrogels share shear thinning behavior. Oscillatory tests showed that the strength of the hydrogel network increases with the crosslinker increase, and decreases at low polymer concentrations. The hydrogels were thixotropic materials with a slow time of structural restoration after breakage. Finally, by analyzing the creep recovery data, the hydrogel responses were all fitted to the Burger model. Overall, it was demonstrated that the presence of essential oil in the proposed hydrogels does not affect the mechanical characteristics of the materials, which are mainly influenced by the concentration of polymer and calcium as a crosslinker.
Highlights
The study of polymers for functional soft materials has advanced rapidly
In light of the current increasing interest in composite hydrogels, here we present a study on the rheological characterization of hydrogels prepared from nanodispersions made of an essential oil stabilized in alginate aqueous suspensions by a nonionic surfactant: Tween 80
The aspect of the hydrogel formed from the alginate-based nanodispersions is shown in Figure 1, where the vials containing the gels (10 days after the gelification) were placed in horizontal position to display the different gel/air interface profile
Summary
Among the various polymers used, alginate is one of the most representative. A great number of applications have been proposed for alginate, ranging from delivery systems, biosensors, soft actuators, and food technology [1,2,3,4,5,6]. The emulsion/dispersion technology frequently uses an internal gelation process for designing alginate particles [7]. Nanoemulsions or nanodispersions represent a strategy for solubilizing lipophilic molecules in aqueous media and designing new products with enriched functionalities [8]. The dispersed phase of oil in water nanoemulsions is made of oil droplets, and the addition of a polymer like alginate in the continuous phase gives the systems more stability, due to the thickening agent role of alginate
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