Effects of Amphiphilic Copolymers Bearing Short Blocks of Lipid-Mimetic Units on the Membrane Properties and Morphology of DSPC Liposomes

Amphiphilic, nonionic diblock copolymers based on poly(ethylene glycol) (PEG 2000–5000), comprising short blocks of lipid-mimetic units, where tested for their ability to afford steric stabilization of distearoylphosphathydilcholine:cholesterol liposomes. The copolymers bear 1–4 lipid-mimetic anchors per copolymer chain. Effects on liposomes size depend on copolymer type and content. Cryo-TEM reveals well-separated, intact, predominantly spherical liposomes at copolymer contents up to 5 mol%. A “flat” liposomes fraction occurs upon incorporation of above 7.5 mol% of copolymers bearing 2 or 4 lipid anchors. 5,6-carboxyfluorescein assay indicates lower leakage of stabilized vs. plain liposomes up to concentration 7.5 mol%. Leakage from liposomes with higher copolymer concentration is insignificantly greater.

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