Thermoreversible hydrogel. XVII. Investigation of the drug release behavior for [N-isopropylacrylamide-co-trimethyl acrylamidopropyl ammonium iodide-co-3-dimethyl (methacryloyloxyethyl) ammonium propane sulfonate] copolymeric hydrogels

Abstract

A series of copolymeric hydrogels were prepared from various molar ratios of N-isopropylacrylamide (NIPAAm), trimethyl acrylamidopropyl ammonium iodide (TMAAI), and 3-dimethyl (methacryloyloxyethyl) ammonium propane sulfonate (DMAPS). Results showed that the swelling ratios of these copolymeric hydrogels increased with an increase of TMAAI content. The drug release behavior of the ionic thermosensitive hydrogels related to their ionicity and drug types. Results indicated that the release ratio of caffeine in the hydrogels was not affected by the ionicity of hydrogels, but increased with increasing of the swelling ratio. The anionic solute (phenol red) strongly interacted with cationic hydrogel (very large Kd), so the phenol red release ratio in cationic gels was very low. On the other hand, CV was adsorbed only on the skin layer of the cationic hydrogel because of the charge repulsion, and released rapidly. Therefore the release ratio was highest for cationic hydrogel to cationic drug. In addition, the partition coefficients (Kd) and the drug delivery behavior of the present gels were also investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1592–1598, 2002