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Polymerized liposomes as stable oxygen‐carriers
Author(s) -
Hayward James A.,
Levine Daniel M.,
Neufeld Lawrence,
Simon Sanford R.,
Johnston David S.,
Chapman Dennis
Publication year - 1985
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(85)81255-2
Subject(s) - liposome , oxygen , polymerization , chemistry , biophysics , chemical engineering , biochemistry , polymer , biology , organic chemistry , engineering
We have produced a surrogate erythrocyte (‘hemosomes’) by encapsulating human hemoglobin in polymerized vesicles composed of diacetylenic phospholipids plus or minus cholesterol. Hemoglobin (in the presence or absence of allosteric effectors) was encapsulated by a freeze‐thaw method in large, unilamellar vesicles composed of monomeric lipids. Entrapment was demonstrated by molecular‐sieve chromatography. Brief irradiation with ultraviolet light produced polymeric hemosomes with polymerization kinetics and conversions similar to liposomes in the absence of protein. Photo‐induced oxidation of the heme was eliminated or severly limited by a combination of prior ligation with CO and the maintenance of high intravesicular hemoglobin concentrations (5–10 mM internal hemoglobin). The inclusion of allosteric effectors within polymerized hemosomes facilitated near‐quantitative conversion to the oxy‐HbA form. Gas permeability of monomeric and polymeric hemosomes was demonstrated by spectroscopic methods. Reversible spectral shifts, corresponding to oxygenation‐deoxygenation, were obtained after brief evacuation and exposure to oxygen or nitrogen. The gas permeability of polymerized hemosomes appears sufficient for the vesicles to act as oxygen carriers in vivo, a notion that is strengthened by their apparent hemocompatibility.