Abstract
Cholesterol is crucial to the mechanical properties of cell membranes that are important to cells’ behavior. Its depletion from the cell membranes could be dramatic. Among cyclodextrins (CDs), methyl beta cyclodextrin (MβCD) is the most efficient to deplete cholesterol (Chol) from biomembranes. Here, we focus on the depletion of cholesterol from a C16 ceramide/cholesterol (C16-Cer/Chol) mixed monolayer using MβCD. While the removal of cholesterol by MβCD depends on the cholesterol concentration in most mixed lipid monolayers, it does not depend very much on the concentration of cholesterol in C16-Cer/Chol monolayers. The surface pressure decay during depletion were described by a stretched exponential that suggested that the cholesterol molecules are unable to diffuse laterally and behave like static traps for the MβCD molecules. Cholesterol depletion causes morphology changes of domains but these disrupted monolayers domains seem to reform even when cholesterol level was low.
Highlights
In this work, we study the removal and depletion of cholesterol from a C16-Cer/Chol mixed monolayer using MβCD
Any loss of material due to the depletion of cholesterol by the MβCD would result in the decay in surface pressure, and a change in domain morphology will be detected through real-time Brewster Angle Microscope (BAM) imaging
The efficacy of the depletion should be reflected in the rate of decay of the surface pressure
Summary
We study the removal and depletion of cholesterol from a C16-Cer/Chol mixed monolayer using MβCD. We selected MβCD among the other members of cyclodextrin (CD) families (e.g. α-CD, β-CD, γ-CD, natural β-CD and hydroxypropyl-β-CD), because it has been reported that MβCD deplete efficiently cholesterol from mixed lipids domains[13,14,15]. After we inject the MβCD into the subphase and to a final concentration of 1 mM, we monitor the monolayer behavior through a Brewster Angle Microscope (BAM). The formation of MβCD/Chol inclusion-complex as well as the consequent removal of cholesterol into the water subphase are expected to be reflected through the change in surface pressure values and domains shape changes. Any loss of material due to the depletion of cholesterol by the MβCD would result in the decay in surface pressure, and a change in domain morphology will be detected through real-time BAM imaging. Unlike earlier works where the monolayers were compressed at a rather high rate of 20 or 50 mm/min, which was detrimental to the equilibrium of the monolayer, we will compress our film at a much lower rate of 1 mm/min so that the film would be able to equilibrate and the surface pressure final value is steady[20,42,43,44,45]
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