Cholesterol in Liposomes

Posted on July 02, 2019

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The isolation of cholesterol was first performed by Dr. Francois Poulletier de la Salle in 1758. Cholesterol was first named in 1815, by Michel Chevruel—he recognized that this fatty substance from the gallstones couldn’t be saponified. He named it “cholesterine,” derived from “chole,” meaning bile, and “stereos,” meaning solid.

What Are the Benefits of Including Cholesterol in Liposomes?

Cholesterol can fill in the gaps left by the imperfect packing of other lipid species. It’s a membrane constituent widely found in biological systems and serves the unique purpose of modulating membrane fluidity, elasticity, as well as permeability. Cholesterol serves the same purpose in model membranes.

What Are the Disadvantages?

Including cholesterol in your liposomes can present certain problems when used in human pharmaceuticals. High purity sources that are meant for clinical applications aren’t widely available, and the sources that are available derive their cholesterol mainly from egg or wool grease. Animal sources are potentially unsuitable for human pharmaceuticals because of the threat of viral contamination.

It’s also important to note that cholesterol is readily oxidized. This can create stability problems for lipid-based drug products, as some oxidation by-products can be toxic in biological systems. 25-hydroxy cholesterol, 7-keto-cholesterol, 7a- and 7B-hydroxycholesterol, cholestane-3B, 5a, 6B-triol and the 5- and 7-hydroperoxides—these by-products were found in a concentrate whose activity caused aortic smooth muscle cells to die. This suggests that results from studies on atherosclerosis and involving experimental animal diets could be ambiguous, because of the potential presence of oxidized sterols.

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TopFluor cholesterol possesses superior photo-physical properties, including a high molar extinction coefficient and quantum yield when compared to Dansyl or NBD fluorophores. This bright, fluorescent analog can be used to visualize sterol trafficking in living cells, using an excitation or emission of 495 nm/503 nm.

PhotoClick cholesterol is a clickable, photoreactive sterol probe meant to use in combination with quantitative mass spectrometry to globally map cholesterol-protein interactions directly in living cells. This is a UV-activatable, cross-linking diazirine group that reacts with proteins. The sterol also contains an alkyne group for incorporation of reporter and affinity tags through click-chemistry.

Cholesterol-d7 is a deuterium labeled lipid. It’s also available in a formulation of the SPLASH ™ LipidoMix ™ Standard. It includes all major lipid classes, at ratios relative to human plasma. This allows one easy internal standard solution to be added every sample. For more information on our products and processes, contact Avanti today!