Preparation and characterization of OSA/CS core–shell microgel: in vitro drug release and degradation properties

Cationic polymers have been widely used as drug delivery systems. Herein, an oxidized sodium alginate/chitosan (OSA/CS) core–shell microgel was prepared via water-in-oil emulsion method. Morphological properties of the resulting microgel were determined by transmission electron microscopy, hydrodynamic diameter of the microgel was characterized by dynamic light scattering. The objective of this work was to achieve the colon-specific delivery of an antiulcerative colitis drug using a fully nontoxic carrier. 5-aminosalicylic acid (5-ASA) was chosen as a model drug, which is rapidly absorbed before entering the colon, thus it is necessary to develop a colon-specific delivery system for it. The in vitro drug release profile was established in buffer solutions with 0.1 M HCl/NaCl (pH 1.2) and 0.1 M phosphate buffered saline (pH 7.4) at 37 °C. The results indicated that this OSA/CS core–shell microgel inhibited the release of 5-ASA in stomach to a certain extent and is degradable in physiological conditions. Due to the excellent biocompatible nature of CS and OSA, this core–shell microgel has good biocompatibility and may have potential applications in oral controlled drug delivery systems.