Stabilization of small unilamellar DMPC-liposomes by uncharged polymers |
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Authors: | F L Grohmann F Csempesz M Szögyi |
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Institution: | Department of Colloid Chemistry E?tv?s University P.O. Box 32 H-1518 Budapest 112 Hungary, HU Institute of Biophysics Semmelweis Medical University Puskin u. 9, Budapest H-1088 Hungary, HU
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Abstract: | Polymer-free and polymer-bearing small unilamellar (SUV) liposomes from dimyristoyl-phosphatidylcholine (DMPC) were prepared
under standardized conditions. Polymer-bearing liposomes were formed by incorporating an uncharged polymer hydrolyzed poly(vinyl
alcohol) (PVA), poly(vinyl alcohol-co-vinylacetal) (PVA-Al), poly(vinyl alcohol-co-vinyl propional) (PVA-Prol) poly(vinyl
alcohol-co-vinyl butiral) (PVA-Bul) copolymer or poly(vinyl pyrrolidone) (PVP)] into the membrane bilayer of vesicles. The
kinetic (long-term) stability of the liposome dispersions stored in distilled water, in physiological NaCl solution and at
various pH values, respectively, were studied. The physical stability of vesicles was tested by measuring the size and the
zeta potential of liposomes by means of a Malvern Zetasizer 4 apparatus.
It was shown that most of these polymers are effective steric stabilizers for the DMPC-liposomes. Among the polymers, the
PVA-Bul and PVA-Prol copolymers and the PVP of high molecular mass exhibited the most efficient stabilizing effect at each
pH studied, indicating that the formation of a relatively thick polymer layer around the lipid bilayers ensures an enhanced
and prolonged physical stability of liposomes. Also, the butiral or propional side chain in the PVA-based copolymers presumably
promotes the anchoring of macromolecules to the vesicles. Using these macromolecules, the colloidal interactions between vesicles
can be modified and so the physical stability of liposomes and the kinetic stability of liposome dispersions can also be controlled.
Received: 20 May 1997 Accepted: 03 September 1997 |
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Keywords: | DMPC-liposomes size distribution uncharged polymers kinetic stability photon correlation spectroscopy |
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