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Conflict of Interest: In relation to this article, we declare that there is no conflict of interest.

Publication history: Received July 5, 2007
Accepted July 25, 2007

This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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pH-dependent release property of dioleoylphosphatidyl ethanolamine liposomes

Seong Min Cho Hyeon Yong Lee Jin-Chul Kim^†

School of Biotechnology & Bioengineering and Institute of Bioscience and Biotechnology, Kangwon National University, 192-1, Hyoja 2-dong, Chunchon, Gangwon-do 200-701, Korea

jinkim@kangwon.ac.kr

Korean Journal of Chemical Engineering, March 2008, 25(2), 390-393(4), 10.1007/s11814-008-0066-6

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Abstract

pH-sensitive liposomes were prepared by a detergent removal method. Dioleoylphosphatidylethanolamine (DOPE) and cholesteryl hemisuccinate (CHEMS) were combined for the preparation of the liposomes so that the molar ratios of DOPE to CHEMS are 9/1, 8/2, 6/4 and 5/5. On transmission electron micrographs, hundreds of nm sized - multilamella vesicles were observed. The degrees of fluorescence quenching were approximately 70-80%, indicating that closed vesicles were formed. According to the results of the pH-dependent release experiment with the liposome composed of DOPE/CHEMS (5/5), no significant release was observed in the pH region ranging from 6 to 8. At pH of 5, an appreciable amount of calcein was released. The patterns of pH-dependent releases from liposomes composed of DOPE/CHEMS (6/4) and DOPE/CHEMS (8/2) were almost the same as those from liposomes composed of DOPE/CHEMS (5/5). With the liposomes composed of DOPE/CHEMS (9/1), unlike the other liposomes described above, almost 90% release was observed at pH 6. In this case, since the amount of a complementary molecule, CHEMS, is relatively small, the liposomes would be subjective to destabilization even at a small change in the degree of deionization of the carboxylic group. This may explain why the liposome of DOPE/CHEMS (9/1) exhibits a significant release at a relatively high pH, pH 6.0.

Keywords

Liposome Dioleoylphosphatidylethanolamine Cholesteryl Hemisuccinate pH-sensitive Release

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