Swelling behaviour is one of the important properties of hydrogel-based drug
delivery systems, which always affects the diffusion of solvent into and release
of drugs from drug loaded microcapsules. In this study, the swelling behaviour
of alginate-chitosan beads at acidic and basic conditions, to simulate gastric and intestinal
media, were investigated. Spherical hydrogel beads were prepared by addition of
aqueous sodium alginate and alginate-N,O-carboxymethyl chitosan (NOCC) solutions
into CaCl2 solution. These hydrogel beads were then transferred into a chitosan solution
to obtain chitosan coated beads. The effect of concentration of calcium chloride,
residence time for ionic cross-linking, concentration of chitosan, addition of NOCC into
alginate solution, coating of alginate-NOCC by chitosan as well as drying method on
the swelling behaviour of the alginate-chitosan beads was studied. It was found that
swelling degree of the air-dried and chitosan coated beads was lower than that for
freeze-dried and uncoated beads, respectively. In addition, the presence of NOCC in
the network resulted in reducing swelling of hydrogel beads. Swelling degree of hydrogels
in basic media (pH 7.4) was also much higher than that in acidic media (pH 1.2).
Thus, alginate-NOCC-chitosan beads are good candidate to be studied as colon-specific
drug delivery systems.
INTRODUCTION
Chitosan is a natural polysaccharide
obtained via deacetylation of
chitin that