Modification of liposome surface with pH-responsive polyampholytes for the controlled-release of drugs

Ampholytic polymers comprised of 2-(diethylamino)ethyl methacrylate (DEAEMA) and acrylic acid (AA) in varying molar ratios were used to modify egg yolk phosphatidylcholine (EYPC) liposomes previously encapsulated with pyranine. The modified EYPC liposomes were found to be pH responsive. The critical pH values at which the pyranine release from these liposomes at 37 A degrees C were observed to decrease with increasing DEAEMA content in the polymers. Explanations were given for these phenomena.