Swelling characteristics and drug delivery properties of nifedipine-loaded pH sensitive alginate–chitosan hydrogel beads



The aim of the present work was to investigate the swelling behavior and in vitro release of nifedipine from alginate–chitosan hydrogel beads. Structure and surface morphology of the hydrogel were characterized by FTIR and SEM, respectively. Alginate–chitosan mixed beads and alginate–chitosan coated beads were prepared by ionic gelation method. The swelling ability of the beads and in vitro release of nifedipine in simulated gastric fluid (pH 1.5) and different phosphate buffer solutions (pH 2.5, 5.0, 6.8, 7.4, and 8.0) were found to be dependent on the presence of the polyelectrolyte complex between chitosan and alginate. The amount of nifedipine released from the mixed beads at pH 1.5 was relatively low (42%), whereas this value approached to 99% at pH 6.8. In comparison with the mixed beads, the released nifedipine from the coated beads was minimal at pH 1.5 (18%), whereas ∼99% nifedipine was released at pH 6.8. The results suggested that the coated beads can hold drug better at low pH than the mixed beads and show excellent pH sensitivity. Therefore, the alginate–chitosan coated beads could be a suitable polymeric carrier for drug delivery in the intestinal tract. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008