The effect of methacrylation on the behavior of Gum Arabic as pH-responsive matrix for colon-specific drug delivery

Abstract

Hydrogels of a natural polysaccharide composed of Gum Arabic (GA) are appropriate materials for drug delivery, since they are water soluble, nontoxic and biocompatible. In this work, the effect of methacrylation on the properties of GA as pH-responsive hydrogel has been evaluated. Modified Gum Arabic (M-GAx), with different degrees of substitution, has been obtained by using different percentages of glycidyl methacrylate (x). It was observed that playing with the x value, gels with different properties have been found: since weak gels to gels with a dual responsive mode. Both gels show non-toxicity against Caco-2 cells. The effects of degree of substitution (DS) and pH on swelling index (SI) were also been studied by using simulated gastric and intestinal fluids through a 22 factorial design. These fluids show pH values below (2) and above (ca. 7) the pKa of M-GA (around 4). The SI increases with an increase of pH and with a decrease in the DS, being predominant the latter factor. Furthermore, the release kinetics of curcumin, used as a model drug, from hydrogel matrices constituted by M-GAx and curcumin-α-cyclodextrin complexes have been carried out. The mechanism, the cumulative release, and the kinetics of curcumin release depend also on the pH and on the DS of M-GAx. This has been discussed in terms of release models with the help of SEM analysis. Our results show that a specific GA hydrogel matrix can be designed by using a proper methacrylation for a given application and, specifically, for colon-specific drug delivery.