title: Preparation of long-circulating immunoliposomes using PEG-cholesterol conjugates: effect of the spacer arm between PEG and cholesterol on liposomal characteristics.
abstract: Poly(ethylene glycol)-coated liposomes were prepared with two new synthesised pegylated cholesterol (Chol) derivatives linked via carbamate bond. Poly(ethylene glycol) (PEG) was directly linked to Chol (PEG-Chol) or through a space arm of diaminebutane (PEG-L-Chol). In buffer, the physicochemical properties of PC/Chol liposomes (2/1, molar ratio) containing up to 10 mol% of pegylated Chol derivatives did not change significantly and the PEG layer at liposome surface inhibited the agglutination of biotin-liposomes induced by streptavidin. On the other hand, in serum, PEG-L-Chol seemed to reduce the interactions of liposomes with serum proteins, much more than PEG-Chol. The low steric hindrance of PEG-Chol derivative may be due to the slow conformational transition rate of the polymer, since PEG may be deeper located in the membrane. The coupling efficiency of the ligand to the functionalised amino group at the polymer end was also affected, but, its antigen-binding activity was preserved. The basic physical-chemical characteristics studied in this work are relevant to assess the application of pegylated Chol liposomes as drug delivery systems.
authors.affiliation: Faculty of Chemistry, Department of Biochemistry and Molecular Biology, University of Barcelona, Martí i Franques, 1, E-08028 Barcelona, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Carrion
authors.forename: J C
authors.initials: JC
authors.lastname: Domingo
authors.forename: M A
authors.initials: MA
authors.lastname: de Madariaga
mesh_terms: D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000276:immunology*; D000937:Antigen-Antibody Reactions / Q000187:drug effects; D018952:Antigens, CD34 / Q000276:immunology; D001798:Blood Proteins / Q000378:metabolism; D002784:Cholesterol / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000494:pharmacology; D003432:Cross-Linking Reagents / Q000737:chemistry; D016503:Drug Delivery Systems; D006801:Humans; D008081:Liposomes / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D010539:Permeability / Q000187:drug effects; D010714:Phosphatidylethanolamines / Q000737:chemistry / Q000494:pharmacology; D010743:Phospholipids / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry* / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects
chemical_list: D000911:Antibodies, Monoclonal; D018952:Antigens, CD34; D001798:Blood Proteins; D003432:Cross-Linking Reagents; D008081:Liposomes; D010714:Phosphatidylethanolamines; D010743:Phospholipids; C118255:polyethylene glycol-cholesterol; C095031:pyridyldithiopropionoylamino-poly(ethylene glycol)-distearoylphosphatidylethanolamine; D011092:Polyethylene Glycols; D002784:Cholesterol