Investigation of water uptake behavior and stability of calcium alginate/chitosan bi-polymeric beads: Part-1

This study describes a detailed investigation of swelling and degradation behavior of ionically cross-linked sodium alginate/chitosan bi-polymeric beads in the environment of varying pH to mimic transition of oral dosage form from mouth to colon. The bead sample S1, prepared by complex coacervation was found to be stable for nearly 320 ± 12 min in the media of varying pH. The variation in amount of chitosan or cross-linking with Al3+ ions did not result in any enhancement in their stability. However, using 6% sodium alginate solution the beads could be stabilized for nearly 10 h. The formation of multilayer beads (S2, S3 and S4) resulted in an drastic increase in the stability of beads. The mechanism of water uptake, as studied for the sample S1 indicated ion exchange process between Ca2+ ions present in polyguluronate and polymannuronate blocks of alginate and Na+ ions present in phosphate buffer medium. This was further confirmed by linear nature of plot obtained between fractional water uptake and time1/2.