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In vitro characterization of a novel polymeric-based pH-sensitive liposome system

Authors
  • Zignani, Monia
  • Drummond, Daryl Clark
  • Meyer, Olivier
  • Hong, Keelung
  • Leroux, Jean-Christophe
Type
Published Article
Journal
Biochimica et Biophysica Acta (BBA) - Biomembranes
Publisher
Elsevier
Publication Date
Jan 01, 2000
Accepted Date
Nov 16, 1999
Volume
1463
Issue
2
Pages
383–394
Identifiers
DOI: 10.1016/S0005-2736(99)00234-5
Source
Elsevier
Keywords
License
Unknown

Abstract

This study demonstrates rapid and pH-sensitive release of a highly water-soluble fluorescent aqueous content marker, pyranine, from egg phosphatidylcholine liposomes following incorporation of N-isopropylacrylamide (NIPA) copolymers in liposomal membranes. The pH-sensitivity of this system correlates with the precipitation of the copolymers at acidic pH. In vitro release can be significantly improved by increasing the percentage of anchor in the copolymer and thus favoring its binding to the liposomal bilayer. In the case of liposomes containing a poly(ethylene glycol)–phospholipid conjugate, the insertion of the pH-sensitive copolymer in the liposomal membrane appears to be sterically inhibited. Dye release from these formulations at acidic pH can still be achieved by varying the anchor molar ratio and/or molecular mass of the polymers or by including the latter during the liposome preparation procedure. Removal of unbound polymer results in decreased leakage only when the copolymer is inserted by incubation with preformed liposomes, but can be overcome by preparing liposomes in the presence of polymer. Aqueous content and lipid mixing assays suggest contents release can occur without membrane fusion. The results of this study indicate that the addition of pH-sensitive copolymers of NIPA represents promising strategy for improving liposomal drug delivery.

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