Enteric-coated Ca-alginate hydrogel beads: a promising tool for colon targeted drug delivery system

Abstract

Enteric coating of hydrogel beads is an effective approach to resolve the drug entrapment problem reported in previous studies. In the present study, microencapsulation of drug in hydrogel beads with extrusion-dripping technique was used for the improvement of the drug entrapment efficiency. Calcium chloride dehydrate was used as a cross-linking agent and oil-in-oil solution of eudragit S-100 was used as coating material while diclofenac sodium was used as a model drug. Optical microscopy, scanning electron microscopy, weight, elemental, and size variation of prepared hydrogels beads were analyzed and found within the acceptable limits. The drug loading and release studies of the coated beads were evaluated. Retardation of the model drug in gastric and intestinal pH environment until 8 h was observed which made the prepared hydrogels more targeted and colon-specific. In acidic pH 1.2, negligible percentage release was observed, whereas at pH 7.4, 98% diclofenac sodium was estimated after 8 h. In vitro release, kinetic studies proved that concentration-dependent release behavior of diclofenac sodium followed Fick’s law of diffusion in coated form, while non-Fickian behavior was observed in uncoated beads. Prepared hydrogel beads may be used as a promising tool for sustained release of drug targeting colon.