Effects of cholesterol on the anionic magnetite nanoparticle-induced deformation and poration of giant lipid vesicles.

We have investigated the effects of cholesterol on the deformation and poration of giant unilamellar vesicles (GUVs) induced by anionic magnetite nanoparticles (NPs). Negatively charged lipid, neutral lipid, and cholesterol were used to prepare the charged GUVs (surface charge density of membranes - 0.16 C m), while only neutral lipid and cholesterol were used to prepare the neutral GUVs. Cholesterol content varied from 0 to 40 mole% for preparing the biologically relevant membranes. The degree of deformation has been characterized by compactness, the value of which remains at 1.0 for spherical GUVs. The value of compactness increases with time for both membranes, but this increase depends on cholesterol content. The average compactness decreases with cholesterol content, and at 60 min, the values are 1.280 ± 0.002 and 1.131 ± 0.010 for 0 and 40 mole% cholesterol containing charged GUVs. The average compactness is relatively lower for neutral GUVs for the corresponding cholesterol. Membrane poration has been investigated by the leakage of calcein, which indicates a two-state transition model. The fraction of deformation is higher for charged GUVs than for neutral ones, while the fraction of poration shows the opposite result. Both the fractions decrease with cholesterol content.