Hydrogel of β-cyclodextrin-Grafted Polyethyleneimine: pH-Sensitive Release

Novel pH-sensitive hydrogels were prepared by grafting β-cyclodextrin (βCD) to polyethyleneimine (PEI) and cross-linking βCD using epichlorohydrin (EPI). While the molar ratio of βCD to PEI was kept to 1:50, the molar ratio of EPI to βCD was varied so that it was 3/1, 5/1, and 10/1. When the EPI to βCD ratio was higher, the degree of equilibrium swelling and the percentage release were lower, possibly due to a higher cross-linking density. The % release of blue dextran was much less than that of fluorescein isothiocyanate-dextran (FITC-dextran). The electrostatic interaction of blue dextran with the hydrogel is believed to suppress the release of the dye. Among the hydrogels prepared in this work, the hydrogel prepared using the βCD to EPI ratio of 1/5 was the most pH sensitive in terms of the degree of swelling and the degree of FITC-dextran release.