Tresylated PEG-sterols for coupling of proteins to preformed plain or PEGylated liposomes.
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 microg protein/mumol 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 degrees C shows stable protein attachment at the liposome surface.
Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology and Biopharmacy, Hermann-Herder-Str. 9, D-79104 Freiburg, Germany.
Thomas
T
Steenpass
Andreas
A
Lung
Rolf
R
Schubert
D006801:Humans; D007700:Kinetics; D008024:Ligands; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008081:Liposomes / Q000097:blood / Q000737:chemistry*; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*; D013261:Sterols / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors
D008024:Ligands; D008051:Lipid Bilayers; D008081:Liposomes; D011506:Proteins; D013261:Sterols; D011092:Polyethylene Glycols