Synergistic effect of thermal and pulsed electric field (PEF) treatment on the permeability of soya PC and DPPC vesicles

Abstract

The permeability change of vesicles composed of soya phosphatidylcholine (PC) and dipalmitoyl phosphatidylcholine (DPPC) encapsulated with 5(6)-carboxyfluorescein (CF) suspended in isotonic sucrose solution under separate or combined thermal and continuous pulsed electric field (PEF) treatments was investigated, respectively. The electric field intensity applied was in the range from 20 to 40kV/cm with total treatment time of 1.2ms, and thermal treatments were conducted at temperatures from 15 to 65°C. Results indicated that the permeability behavior between DPPC vesicles and soya PC vesicles were quite different under the experimental conditions. Compared to soya PC vesicles, DPPC vesicles were more sensitive to thermal treatments. As the temperature increased to 41°C, the 5(6)-CF release percentage (R) reached almost 100% abruptly. On the other hand, the synergetic effects of PEF and temperature on permeability of two vesicles were apparently different. For soya PC vesicles, the increment degree of R value was almost the same under various combination treatment conditions. However, for DPPC vesicles, it was demonstrated that the lipid bilayers membrane was almost impermeable to CF when the PEF strength was lower than 30kV/cm at 20°C and 20kV/cm at 30°C. As the temperature increased to 38°C, the permeability of DPPC vesicles was significantly increased with increasing PEF intensity, reaching 25.25% at 40kV/cm. Results from the current study could be helpful for better understanding of the underlying mechanism on PEF inactivation as affected by the lipid composition of cell membrane and its phase transition temperature.