Quantification of pulsed electric field for the rupture of giant vesicles with various surface charges, cholesterols and osmotic pressures

Effects of polyethylene glycol-grafted phospholipid on the anionic magnetite nanoparticles-induced deformation and poration in giant lipid vesicles

The hydrophilic polymer polyethylene glycol-grafted phospholipid has been used extensively in the study of artificial vesicles, nanomedicine, and antimicrobial peptides/proteins. In this research, the effects of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N- [methoxy (polyethylene glycol)-2000] (abbreviated PEG-DOPE) on the deformation and poration of giant unilamellar vesicles (GUVs)-induced by anionic magnetite nanoparticles (NPs) have been investigated. For this, the size of the NPs used was 18 nm, and their concentration in the physiological solution was 2.00 μg/mL. GUVs were prepared using the natural swelling method comprising 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and PEG-DOPE. The mole% of PEG-DOPE in the membranes were 0, 2, and 5%. The degree of deformation of the GUVs was quantified by the parameter compactness (Com), which is 1.0 for the spherical-shaped GUVs. The value of Com increases with time during the interactions of NPs with GUVs for any concentration of PEG-DOPE, but the rate of increase is significantly influenced by the PEG-DOPE concentration in the membranes. The average compactness increases with the increase of PEG-DOPE%, and after 60 min of NPs interaction, the values of average compactness for 0, 2, and 5% PEG-DOPE were 1.19 ± 0.02, 1.26 ± 0.03 and 1.35 ± 0.05, respectively. The fraction of deformation (Frd) also increased with the increase of PEG-DOPE%, and at 60 min, the values of Frd for 0 and 5% PEG-DOPE were 0.47 ± 0.02 and 0.63 ± 0.02, respectively. The fraction of poration (Frp) increased with the increase of PEG-DOPE, and at 60 min, the values of Frp for 0 and 5% PEG-DOPE were 0.25 ± 0.02 and 0.48 ± 0.02, respectively. Hence, the presence of PEG-grafted phospholipid in the membranes greatly enhances the anionic magnetite NPs-induced deformation and poration of giant vesicles.

All-atom molecular dynamics simulations of the combined effects of different phospholipids and cholesterol content on electroporation

The electroporation mechanism could be related to the composition of the plasma membrane, and the combined effect of different phospholipid molecules and cholesterol content on electroporation has rarely been studied nor conclusions drawn. In this paper, we applied all-atom molecular dynamics (MD) simulations to study the effects of phospholipids and cholesterol content on bilayer membrane electroporation. The palmitoyloleoylphosphatidylcholine (POPC) model, palmitoyloleoylphosphatidylethanolamine (POPE) model, and a 1 : 1 mixed model of POPC and POPE called PEPC, were the three basic models used. An electric field of 0.45 V nm-1 was applied to nine models, which were the three basic models, each with three different cholesterol content values of 0%, 24%, and 40%. The interfacial water molecules moved under the electric field and, once the first water bridge formed, the rest of the water molecules would dramatically flood into the membrane. The simulation showed that a rapid rise in the Z-component of the average dipole moment of the interfacial water molecules (Z-DM) indicated the occurrence of electroporation, and the same increment of Z-DM represented a similar change in the size of the water bridge. With the same cholesterol content, the formation of the first water bridge was the most rapid in the POPC model, regarding the average electroporation time (t ep), and the average t ep of the PEPC model was close to that of the POPE model. We speculate that the differences in membrane thickness and initial number of hydrogen bonds of the interfacial water molecules affect the average t ep for different membrane compositions. Our results reveal the influence of membrane composition on the electroporation mechanism at the molecular level.

Effects of sugar concentration on the electroporation, size distribution and average size of charged giant unilamellar vesicles

We investigated the effects of sugar concentration on the electroporation, size distribution and average size of giant unilamellar vesicles (GUVs). GUVs were prepared from 40 mol% of 1,2-dioleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DOPG) and 60 mol% of 1, 2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) lipids. Pulsed electric field was applied to the 40%DOPG/60%DOPC-GUVs and it induced lateral electric tension (σ_c) in the membranes of vesicles. The σ_c-induced probability of rupture (P_pore) and the rate constant of rupture (k_p) of GUVs under the sugar concentration, c = 40, 100 and 300 mM, were determined. Both the P_pore and k_p increased with the increase of σ_c, but higher tension was required to generate the same values of P_pore and k_p with increasing c. We also investigated average sizes of GUVs from the size distribution of vesicles under various sugar concentrations. With the increase of c, the peak of the size distribution histograms shifted to the region of smaller vesicles. The average size decreased 1.6-fold when c increased from 10 to 300 mM. These investigations help to understand various biomedical, biophysical, and biochemical processes in vesicles and cells. Electroporation, size distribution and average size of charged GUVs were investigated under various sugar concentrations. The sugar concentration influences the electroporation of vesicles and the average size of GUVs.