Effects of cholesterol on the magnetite nanoparticles induced deformation and poration of giant lipid vesicles

Abstract

Cholesterol (chol) is one of the important elements in the cell membranes. We have been investigated the effects of chol on the deformation and poration of cell mimetic giant unilamellar vesicles (GUVs) induced by anionic magnetite nanoparticles (NPs) of average size 18 nm. Lipids and chol are used to prepare the charged and neutral GUVs in which chol varies from 0 to 40 mole% for biologically relevant membranes. The degree of deformation such as compactness remains 1.0 for spherical shaped GUVs, and it increases with time for both charged and neutral membranes. The average compactness decreases with chol, and at 60 min, the values are 1.280  0.002 and 1.131  0.010 for 0 and 40% chol containing charged membranes, respectively, while 1.269  0.008 and 1.099  0.004 for 0 and 40% chol containing neutral membranes, respectively. The values of fraction of deformation are 0.63 ± 0.02 for 0% chol, and 0.24 ± 0.01 for 40% chol in charged membranes, while 0.44 ± 0.02 for 0% chol, and 0.21 ± 0.003 for 40% chol in neutral membranes at 60 min. Membrane poration has been investigated by the leakage of encapsulating fluorescent probe (calcein) of GUVs. The values of fraction of poration are 0.24 ± 0.02 for 0% chol and 0.04 ± 0.01 for 40% chol containing charged membranes, while 0.28 ± 0.06 for 0% chol and 0.05 ± 0.01 for 40% chol containing neutral membranes at 50 min. Both the fraction of poration and fraction of deformation decrease with chol in the membranes. The fraction of deformation is higher for charged GUVs than neutral ones, while the fraction of poration shows the opposite result. The possible mechanism for vesicle deformation and lipid membrane poration has been discussed.