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Interaction of poloxamine block copolymers with lipid membranes: Role of copolymer structure and membrane cholesterol content.

Colloids and surfaces. B, Biointerfaces (2015-06-27)
Isabel Sandez-Macho, Matilde Casas, Emilio V Lage, M Isabel Rial-Hermida, Angel Concheiro, Carmen Alvarez-Lorenzo
ABSTRACT

Interactions of X-shaped poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO) block copolymers with cell membranes were investigated recording the π-A isotherms of monolayer systems of dipalmitoylphosphatidylcholine (DPPC):cholesterol 100:0; 80:20 and 60:40 mol ratio and evaluating the capability of the copolymers to trigger haemolysis or to protect from haemolytic agents. Four varieties of poloxamine (Tetronic 904, 908, 1107 and 1307) were chosen in order to cover a wide range of EO and PO units contents and molecular weights, and compared to a variety of poloxamer (Pluronic P85). The π-A isotherms revealed that the greater the content in cholesterol, the stronger the interaction of the block copolymers with the lipids monolayer. The interactions were particularly relevant at low pressures and low lipid proportions, mimicking the conditions of damaged membranes. Relatively hydrophobic copolymers bearing short PEO blocks (e.g., T904 and P85) intercalated among the lipids expanding the surface area (ΔGexc) but not effectively sealing the pores. These varieties showed haemolytic behavior. Oppositely, highly hydrophilic copolymers bearing long PEO blocks (e.g., T908, T1107 and T1307) caused membrane contraction and outer leaflet sealing due to strong interactions of PEO with cholesterol and diamine core with phospholipids. These later varieties were not haemolytic and exerted a certain protective effect against spontaneous haemolysis for both intact erythrocytes and cholesterol-depleted erythrocytes.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Cholesterol, Sigma Grade, ≥99%
Sigma-Aldrich
Chloroform, anhydrous, ≥99%, contains 0.5-1.0% ethanol as stabilizer
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Chloroform, anhydrous, contains amylenes as stabilizer, ≥99%
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Cholesterol, powder, BioReagent, suitable for cell culture, ≥99%
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1-Pentanol, ACS reagent, ≥99%
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SyntheChol® NS0 Supplement, 500 ×, synthetic cholesterol, animal component-free, aqueous solution, sterile-filtered, suitable for cell culture
SAFC
Cholesterol, Plant-Derived
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Cholesterol, from sheep wool, ≥92.5% (GC), powder
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1-Pentanol, puriss. p.a., ACS reagent, ≥99.0% (GC)
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Amyl alcohol, ≥99%, FG
Supelco
Chloroform, suitable for HPLC, ≥99.8%, contains 0.5-1.0% ethanol as stabilizer
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Chloroform, ≥99%, PCR Reagent, contains amylenes as stabilizer
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1,2-Dipalmitoyl-rac-glycero-3-phosphocholine, ~99%
Sigma-Aldrich
Chloroform, ACS reagent, ≥99.8%, contains 0.5-1.0% ethanol as stabilizer
SAFC
Cholesterol, from sheep wool, Controlled origin, meets USP/NF testing specifications
Sigma-Aldrich
Chloroform, ACS reagent, ≥99.8%, contains amylenes as stabilizer
Supelco
Chloroform, suitable for HPLC, ≥99.8%