Preparation and characterization of novel cationic copolymer hydrogels with pH sensitivity and thermo sensitivity

Cationic hydrogels were synthesized through the copolymerization of N-isopropylacrylamide and dimethylamitioethylniethacrylate. N,N'-Methylenebisacrylamide was used as a crosslinking agent, and sodium bisulfite/ammonium persulfate was used as art initiator. The equilibrium and dynamic swelling properties were investigated to reveal the pH sensitivity and thermosensitivity of the hydrogels. The conclusion was drawn that the prepared cationic hydrogels demonstrated critical sensitivity at 37 degrees C and pH 7.0-8.0 and that the stronger the acidity was of the buffered solution, the shorter the equilibrium swelling time was of the hydrogels. Drug-release experiments in vitro were carried out at 37 degrees C (close to body temperature), at pH 1.4 (close to the pH of the stomach), and at pH 7.4 (close to the pH of the intestine). The release results indicated that the drug (chloramphenicol) was released more rapidly from the prepared hydrogel in a pH 7.4 buffered solution than in a pH 7.4 one, and this was consistent with the results predicted from the experiments of the swelling kinetics. Moreover, the drug-release process was confirmed by scanning electron micrographs of the hydrogels embedded with chloramphenicol. (c) 2006 Wiley Periodicals, Inc.