[en] Purpose: Print 3G, a peptidic antagonist of oncoproteins involved in breast cancer, was encapsulated in PEGylated liposomes. Seeing its temperature instability, this peptide must be stored at – 20°C. In this study, the cryoprotection of PEGylated liposomes was investigated to ensure their stability in terms of size and retention capacity when frozen. Calcein, a self-quenching fluorescent marker encapsulated in liposomes, was used as a tracer of liposome integrity. The release of calcein was studied before and after freezing, with or without cryoprotectants at several concentrations.
Methods: Unilamellar vesicles made of SPC:CHOL:mPEG-750-DSPE (47:47:6) or SPC:CHOL:mPEG-2000-DSPE (47:47:6) were prepared by the film evaporation method. Size of the liposomes dispersions containing a cryoprotectant (sucrose, trehalose or lysine) at various concentrations were measured by photon correlation spectroscopy before and after freezing. From these results, two cryoprotectants (at the best molar ratio of sugar-to-lipid) were chosen for future experiments with calcein. Its release from the inner cavity of liposomes was measured fluorometrically before and after freezing, with or without cryoprotectant. The percentage of calcein retained was determined at excitation and emission wavelengths of 490 and 520 nm, respectively. The liposomes were prepared with cryoprotectant either only outside the vesicles or both inside and outside.
Results: In regards to the results obtained with PCS, sucrose and trehalose (molar ratio of sugar-to-lipid = 4) were selected for calcein experiments. The best results in terms of retention efficiency were obtained using cryoprotectant inside and outside the vesicles. Liposomes containing mPEG-750-DSPE show the best retention efficiency after freezing with trehalose (75.42 ± 2.39 %, n=3) in comparison with sucrose (62.16 ± 4.34 %, n=3). Liposomes containing mPEG-2000-DSPE doesn’t show significant difference (T-Test) between trehalose (84.27 ± 5.05%, n=3) and sucrose (83.38 ± 3.18 %, n=3). In the future experiments, these results will be compared with experiments of frozen liposomes encapsulating Print 3G.
Acknowledgements: This work was supported by the Ministry of the Walloon Region.
Research Center/Unit :
C.I.R.M.
Disciplines :
Pharmacy, pharmacology & toxicology
Author, co-author :
Ducat, Emilie ; Université de Liège - ULiège > Département de pharmacie > Pharmacie galénique
Evrard, Brigitte ; Université de Liège - ULiège > Département de pharmacie > Pharmacie galénique
Piel, Géraldine ; Université de Liège - ULiège > Département de pharmacie > Pharmacie galénique
Language :
English
Title :
STUDY OF PEGYLATED LIPOSOMES CRYOPROTECTION IN TERMS OF RETENTION EFFICIENCY
Publication date :
2008
Number of pages :
A0
Event name :
6th international workshop on drug delivery systems for nanomedecines
Event place :
Liblice, Czechia
Event date :
du 3 au 6 octobre 2008
Audience :
International
Name of the research project :
Peptides antagonistes d'oncoprotéines pour une thérapeutique du cancer du sein
Funders :
DGTRE - Région wallonne. Direction générale des Technologies, de la Recherche et de l'Énergie
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