Novel temperature-sensitive poly[N-isopropylacrylamide-co-2-hydroxyethylacrylate] [P(NIPAAm-HEAc)] colloidal crystals containing beta-cyclodextrin (beta-CD) were prepared. These reversibly tunable supramolecular inclusion complexes display brilliant colors, due to the self-assembly of several structured nanoparticles to form crystal structures. The hydrogels displayed rainbow colors upon the variation of the P-CD concentration and can be made either visible or invisible by simply changing the temperature. The inclusion complexes were characterized using NMR spectroscopy, laser light scattering, UV-visible spectroscopy, and viscometer measurements. Compared with the conventional poly(N-isopropylacrylamide) gel, the beta-CD-incorporated hydrogels in aqueous solution showed a lower critical solution temperature of about 57 degrees C, which can be attributed to the hydrogen bonding between P(NIPAAm-HEAc) included in P-CD and water, which is enhanced by the hydrophilic groups of beta-CD. The use of these materials as drug carriers was also evaluated by making use of their thermo-responsive behavior. The release time of a model drug, 5-fluorouracil (5-FU), from the novel inclusion complexes was prolonged in comparison to that from P(NTPAAm-HEAc) without P-CD. The significance of the present drug delivery system is the mixing of the gel and drug without any chemical reaction at room temperature, resulting in a gelled drug depot for slow and controlled release. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 1680-1689, 2009