Beads composed of alginate, poly(N-isopropylacrylamide) (PNIPAM), the copolymers of N-isopropylacrylamide and methacrylic acid (P(NIPAM-co-MAA)), and the copolymers of N-isopropylacrylamide, methacrylic acid, and octadecyl acrylate (P(NIPAM-co-MAA-co-ODA)), were prepared by dropping the polymer Solutions into CaCl2 solution. The beads were freeze-dried and the release of blue dextran entrapped in the beads was observed in distilled water with time and pH. The degree of release was in the order of alginate bead < alginate/PNIPAM bead approximate to alginate/P(NIPAM-co-MAA) bead < alginaite/P(NIPAM-co-MAA-co-ODA) bead. On the other hand, swelling ratios reached steady state within 20 min, and the values were 200-800 depending on the bead composition. The degree of swelling showed the same order as that of release. Among the beads, only alginate/P(NIPAM-co-MAA-co-ODA) bead exhibited pH-dependent release. At acidic condition, inter- and intraelectrostatic repulsion is weak and P(NIPAM-co-MAA-co-ODA) could readily be assembled into an aggregate due to the prevailing hydrophobic interaction of ODA. Thus, it Could block the pore of bead matrix, leading to a suppressed release. (C) 2008 Wiley Periodicals, Inc.