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Sterol-modified phospholipids: cholesterol and phospholipid chimeras with improved biomembrane properties.

ABSTRACT: We synthesized a family of sterol-modified glycerophospholipids (SML) in which the sn-1 or sn-2 position is covalently attached to cholesterol and the alternative position contains an aliphatic chain. The SML were used to explore how anchoring cholesterol to a phospholipid affects cholesterol behavior in a bilayer. Notably, cholesterol in the SML retains the membrane condensing properties of free cholesterol regardless of the chemistry or position of its attachment to the glycerol moiety of the phospholipid. SMLs by themselves formed liposomes upon hydration and in mixtures between an SML and diacylglycerophospholipids (C14 to C18 chain length) the thermotropic phase transition is eliminated at the SML equivalent of about 30 mol % free cholesterol. Osmotic-induced contents leakage from SML (C14-C18) liposomes depends upon the linkage and position of cholesterol but in general is similar to that observed in 3/2 diacylphosphatidylcholine/cholesterol (mole ratio) liposomes. SML liposomes are exceptionally resistant to contents release in the presence of serum at 37 degrees C. This is probably due to the fact that SML exchange between bilayers is more than 100 fold less than the exchange rate of free cholesterol in the same conditions. Importantly, SML liposomes containing doxorubicin are as effective in treating the murine C26 colon carcinoma as Doxil, a commercial liposome doxorubicin formulation. SMLs stabilize bilayers but do not exchange and hence provide a new tool for biophysical studies on membranes. They may improve liposomal drug delivery in organs predisposed to the extraction of free cholesterol from bilayers, such as the skin, lung, or blood.

SUBMITTER: Huang Z

PROVIDER: S-EPMC2701441 | biostudies-literature | 2008 Nov

REPOSITORIES: biostudies-literature

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Sterol-modified phospholipids: cholesterol and phospholipid chimeras with improved biomembrane properties.

Huang Zhaohua Z Szoka Francis C FC

Journal of the American Chemical Society 20081025 46

We synthesized a family of sterol-modified glycerophospholipids (SML) in which the sn-1 or sn-2 position is covalently attached to cholesterol and the alternative position contains an aliphatic chain. The SML were used to explore how anchoring cholesterol to a phospholipid affects cholesterol behavior in a bilayer. Notably, cholesterol in the SML retains the membrane condensing properties of free cholesterol regardless of the chemistry or position of its attachment to the glycerol moiety of the ...[more]

PMID: 18950160

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Project description:We employed a recently introduced class of sterol-modified lipids (SML) to produce m-PEG-DSPE containing liposome compositions with a range of cis-platinum content release rates. SML have a cholesterol succinate attached to the phosphatidylglycerol head group and a fatty acid at the 2 position. These compositions were compared to the well-studied liposome phospholipid compositions: mPEG-DSPE/Hydrogenated Soy PC/cholesterol or mPEG-DSPE/POPC/cholesterol to determine the effect of the cis-platinum release extent on C26 tumor proliferation in the BALB/c colon carcinoma mouse model. The release rates of cis-platinum from liposomes composed of SML are a function of the acyl chain length. SML-liposomes with shorter acyl chain lengths C-8 provided more rapid cisplatin release, lower in vitro IC50, and were easier to formulate compared to liposomes using traditional phospholipid compositions. Similar to other liposome cis-platinum formulations, the half-life of m-PEG-DSPE SML liposome cisplatin is substantially longer than the free drug. This resulted in a higher tumor cisplatin concentration at 48h post-dosing compared to the free drug and higher Pt-DNA adducts in the tumor. Moreover, the maximum tolerated dose of the liposome formulations where up to four fold greater than the free drug. Using X-ray fluorescence spectroscopy on tumor sections, we compared the location of platinum, to the location of a fluorescence lipid incorporated in the liposomes. The liposome platinum co-localized with the fluorescent lipid and both were non-uniformly distributed in the tumor. Non-encapsulated Cis-platinum, albeit at a low concentration, was more uniformly distributed thorough the tumor. Three liposome formulations, including the well-studied hydrogenated HSPC composition, had better antitumor activity in the murine colon 26 carcinoma model as compared to the free drug at the same dose but the SML liposome platinum formulations did not perform better than the HSPC formulation.

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Dataset Information

Sterol-modified phospholipids: cholesterol and phospholipid chimeras with improved biomembrane properties.

Publications

Sterol-modified phospholipids: cholesterol and phospholipid chimeras with improved biomembrane properties.

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