title: Encapsulation of hemoglobin in non-phospholipid vesicles.
abstract: The efficiency of encapsulating hemoglobin in non-phospholipid liposomes by rapidly mixing hemoglobin with lipids heated above their solid-liquid phase transition temperature was examined. Human hemoglobin was mixed at 55-60 degrees C with a lipid solution containing polyoxyethylene-2 cetyl ether and cholesterol (molar ratio, 3:1) at 60-65 degrees C. Repeated mixing was carried out through a high-shear orifice, followed by rapid cooling and additional mixing. Lipid vesicles were heterogeneous in size, with diameters from approximately 300 nm to 10 microns. The non-encapsulated aqueous phase was removed by centrifugation, and total hemoglobin was determined spectrophotometrically. Encapsulation efficiency was calculated as the percentage of hemoglobin associated with the liposome phase (i.e., encapsulated) as a function of hemoglobin concentration and the aqueous:lipid hydration ratio. Hemoglobin concentrations were varied from 1 to 10 nM (in heme). Aqueous:lipid ratios of 8:1 and 4:1 were tested. Percent encapsulation varied from 13-30%, with the greatest efficiency, i.e., 30%, at a 4:1 hydration ratio of hemoglobin:lipid at 5.6 mM hemoglobin.
authors.affiliation: Blood Cells, Inc., La Jolla, CA.
authors.forename: K D
authors.initials: KD
authors.lastname: Vandegriff
authors.forename: D F
authors.initials: DF
authors.lastname: Wallach
authors.forename: R M
authors.initials: RM
authors.lastname: Winslow
mesh_terms: D001802:Blood Substitutes / Q000008:administration & dosage* / Q000302:isolation & purification; D002784:Cholesterol; D006454:Hemoglobins / Q000008:administration & dosage* / Q000302:isolation & purification; D006358:Hot Temperature; D006801:Humans; D066298:In Vitro Techniques; D008081:Liposomes; D008863:Microspheres; D011092:Polyethylene Glycols; D014867:Water
chemical_list: D001802:Blood Substitutes; D006454:Hemoglobins; D008081:Liposomes; D014867:Water; D011092:Polyethylene Glycols; D002784:Cholesterol