Egg phosphatidylcholine liposomes incorporating hydrophobically modified chitosan: pH-sensitive release.

Egg phosphatidylcholine (EPC) liposomes incorporating hydrophobically modified chitosan (HmCh) were prepared by a sonication method. In order to immobilize chitosan on the surface of EPC liposomes, pentyl chains were covalently attached to chitosan. Following the proton NMR spectrum, the number of pentyl chains per chitosan molecule was calculated to be 2.5. Once the ratio of HmCh to EPC was kept below 1:5, the degrees of fluorescence quenching in the liposomal suspension were greater than 70%, indicating a high yield of liposome formation. No significant release from the liposome was observed in neutral and akali condition. The liposomes started to release their content at pH 6.5, and the release became more extensive as the pH of release medium decreased. The pH-sensitivity of the liposomes in terms of the release strongly depended on the amount of HmCh incorporated in liposomes.