A novel pH-sensitive membrane from chitosan - TEOS IPN; preparation and its drug permeation characteristics

A novel organic-inorganic composite membrane was prepared, using tetra ethy l ortho silicate (TEOS) as an inorganic material and chitosan as an organic compound. Equilibrium and oscillatory swelling studies were conducted to i nvestigate swelling behaviors of the membrane according to the pH of the sw elling medium. Drug permeation experiments were also performed in phosphate buffer solution of the pH of 2.5 and 7.5, respectively. Lidocaine HCl, sod ium salicylate and 4-acetamidophenol were selected as model drugs to examin e the effect of ionic property of drug on the permeation behavior. The effe cts of membrane composition and the external pH on the swelling and the dru g permeation behavior of IPN membrane could be summarized as follows; chito san incorporated into TEOS IPN swelled at pH 2.5 while shrunk at pH 7.5. Th is swelling behavior was completely reversible and the membrane responded r apidly to the change in environmental pH condition. According to swelling b ehavior, an increase in pH from 2.5 to 7.5 yielded an increase in the rate of drug permeation because of the shrinking of the incorporated chitosan in TEOS IPN, while decrease in pH resulted in low permeation rate. The optima l TEOS-chitosan ratio for maximum pH sensitivity existed and drug permeatio n was influenced not only with the external pH but also with the ionic inte ractions between the drug and membrane. (C) 2001 Elsevier Science Ltd. All rights reserved.