Tresylated PEG-sterols for coupling of proteins to preformed plain or PEGylated liposomes |
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Authors: | Thomas Steenpaß |
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Affiliation: | Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology and Biopharmacy, Hermann-Herder-Str. 9, D-79104 Freiburg, Germany |
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Abstract: | A simple and inexpensive method for functionalization of preformed liposomes is presented. Soy sterol-PEG1300 ethers are activated by tresylation at the end of the PEG chain. Coupling of bovine serum albumin as an amino group containing model ligand to the activated lipids can be performed at pH 8.4 with high efficiency. At room temperature, the mixture of sterol-PEG and sterol-PEG-protein inserts rapidly into the outer liposome monolayer with high efficiency (>100 μg protein/μmol total lipid). This method of post-functionalization is shown to be effective with fluid or rigid and plain or pre-PEGylated liposomes (EPC/Chol, 7:3; HSPC/Chol 2:1, and EPC/Chol/MPEG2000-DSPE 2:1:0.16 molar ratios). The release of entrapped calcein upon the insertion of 7.5 mol% of the functionalized sterols is lower than 4%. Incubation of post-functionalized liposomes with serum for 20 h at 37 °C shows stable protein attachment at the liposome surface. |
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Keywords: | BSA, bovine serum albumin Chol, cholesterol DSPE, 1,2-distearoyl-sn-glycero-3-phosphoethanolamine EPC, egg phosphatidylcholine HBS, HEPES-buffered saline HSPC, hydrogenated soy phosphatidylcholine MAL-PEG-DSPE, 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[maleimido-poly(ethyleneglycol)] MPEG2000-DSPE, 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy-poly(ethyleneglycol)-2000] PCS, photon correlation spectroscopy PEG, poly(ethylene glycol) sterol-PEG1300, soy sterol-poly(ethyleneglycol)-1300-ether TEA, triethylamine THF, tetrahydrofuran tresylchloride, 2,2,2-trifluoroethanesulfonylchloride TL, total lipid TLC, thin layer chromatography |
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