Effect of Acidic Medium on Swelling and Release Behaviors of Chitosan-Reinforced Calcium Pectinate Gel Beads

Chitosan-reinforced calcium pectinate (ChCP) gel beads were prepared by ionotropic gelation method. The swelling of ChCP gel beads and release behavior of indomethacin from the beads were investigated and compared with conventional calcium pectinate (CP) gel beads. The factors, such as molecular weight of chitosan, concentration of chitosan, and release medium, which can have a significant effect on the swelling and release behaviors from the beads, were discussed in this study. The mechanical test showed that the ChCP beads have slightly higher strength than that of CP beads. The swelling index of the ChCP beads in acidic medium was much lower than that in neutral medium. The release of indomethacin from ChCP beads under conditions mimicking intestinal transit were evaluated in pH 7.4 Tris buffer. The acid pretreatment caused a faster drug release from ChCP beads. The less swelling in acidic medium and faster drug release of acid-pretreated ChCP beads may be due to the dissolution of chitosan from the beads in acidic medium, as no fluorescence signal was seen at the shell of the beads. The results suggested that the acid, which essentially found in stomach, influenced the swelling and release behaviors of ChCP beads.