Evaluation of the Swelling and Diffusional Behavior of Guar Gum for the Controlled Release of Bio active Agents

摘要

Guar gum is a hydrophilic polymer that has gained attention for the fabrication of matrices for controlled solute release due to its gelling nature and ability to entrap the solute within the gel. It is highly soluble in water, stable over a wide range of temperature, acidic, alkaline and enzymatic conditions. Matrix systems are made of polymeric materials that are swellable in the presence of biological fluids. The powdered solute was distributed uniformly in a matrix of guar gum and directly compressed to form a tablet using a single punch tablet press equipped with a flat-faced tooling (13 mm diameter). A guar gum matrix tablet is cost effective and have broad FDA acceptance. The swelling characteristics of guar gum matrix tablets were studied using three solutes having different solubilities. Thus, methylene blue, caffeine and salicylic acid were used as soluble, highly soluble and acidic compounds. Swelling was assessed by measuring the axial and radial expansion of matrix tablets following exposure to distilled water, acidic and brine media. The mechanisms of solute release and matrix swelling rate were calculated from the dissolution and swelling experiments, respectively. Matrix swelling was related to the intake of a large amount of water and formation of a viscoelastic mass. A rapid absorption of water took place through permeation and capillary action. Solute release kinetics included mainly relaxation rather than diffusion transport. Solute release was also influenced by the presence of ions and pH of the media. The mechanism of solute release from this polymeric matrix mostly conforms to non-Fickian (anomalous) transport. Thus, swelling played an important role to obtain complete solute release within 24 h. Further, the ionic strength of the liquid had a strong effect on the sorption properties of the matrix. Solute release from guar gum matrices was preceded mainly by a combination of swelling and diffusion mechanisms depending on the chemical nature of the solute employed. Kinetics of solute release from these matrices depended mainly on the synchronization of polymer hydration at the moving rubbery/glassy front within the matrix and the rate of solute diffusion.