Effects of vesicle components on the electro-permeability of lipid bilayers of vesicles induced by pulsed electric fields (PEF) treatment

Abstract

In this study, the effects of pulsed electric field (PEF) treatments on the electro-permeability of vesicles made from dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), dioleoyl-sn-glycero-3-phosphocholine (DOPC), Soya phosphatidylcholine (soya PC), cholesterol and a binary mixture of them encapsulated 5(6)-Carboxyfluorescein (5(6)-CF) were investigated, based on the electric field strength of 0–40 kV/cm and treatment time of 0–4.8 ms. Results indicated that the electro-permeability of lipid membrane was directly related to the composition of lipid bilayers membrane of vesicles. As compared to DPPC vesicles, DOPC vesicles were much more sensitive to PEF treatment. For the DOPC vesicles, the 5(6)-CF release percentage (R) was 9.24%, 20.12%, and 30.62% after PEF treatment at 20, 30, and 40 kV/cm for 4.8 ms treatment time, respectively. However, for the DPPC vesicles, it was only 1.84%, 4.02%, and 6.51%, respectively. On the other hand, the electro-permeability of DOPC vesicles was greatly affected by the addition of DPPC. The electro-permeability of DOPC vesicles was decreased sharply with the increase of DPPC molar ratio. Under the PEF treatment with 40 kV/cm and 1.2 ms, it was observed that the R of DOPC vesicles decreased markedly from 27.56% to 9.80% with the molar ratio of DPPC increased from 0 to 40%.For the soya PC vesicles, the R was dropped sharply from 48.13% to 24.11% with the molar ratio of cholesterol increased from 0 to 50%. Raman spectroscopy analysis revealed that the decrease of electro-permeability of soya PC vesicles with the addition of cholesterol was responsible for the incorporating of cholesterol into hydrocarbon partition of lipid bilayers, leading to the order arrangement of hydrocarbon chain of phospholipids, which was resulted an increase in the thickness of bilayers membrane and decrease in the fluidity of bilayers membrane. However, for the mixture of DOPC and DPPC (DOPC/DPPC) vesicles, there has no effect on the conformation of hydrocarbon chain of phospholipids and the fluidity of bilayer membrane of DOPC/DPPC vesicles with the addition of DPPC.