Membranes of microorganisms stressed with pulsed electric fields (PEF) of sufficient intensity and duration can be permanently damaged by irreversible electroporation. Such PEF-induced damage of a bio-membrane can lead to the death of the microorganism; this process facilitates practical applications of PEF for microbial inactivation in liquids and lysis. PEF treatment is considered a “non-thermal” inactivation process: typically the global temperature of liquid samples treated with impulsive electric fields remains below the thermal inactivation threshold. However, intense electric fields may result in the development of local temperature gradients across biological membranes. Thus, it is important to investigate these local heating effects for further understanding and optimisation of PEF treatment of microorganisms.
The present paper aims to model the transient temperature across a biological membrane stressed by intense electrical impulses. The model, developed using COMSOL Multiphysics software, is based on a round cell with a bio-membrane, filled with a highly-conductive fluid (representing cytoplasm) and surrounded by an external liquid (water), which is stressed with pulsed electric fields with a magnitude of 25 kV/cm and duration of 1 µs. This model was used to investigate local heating effects across the cell membrane, and in the cytoplasm and the external liquid. A model pore was then introduced into the membrane, to simulate the electroporation process; this approach was used to investigate potential local heating effects caused by the formation of pores during the PEF process.  
The results obtained show that, during application of the pulsed electric field, the presence of a single pore does not affect the temperature of the external liquid (as compared with no pore case). However, it was shown that this pore, when filled with cytoplasm, undergoes an intensive local heating process, which may help to expand the pore and facilitate electroporation during the PEF treatment. It is also shown that the local temperature inside the pore is affected by its aperture and position in the membrane: the wider the pore, the higher the local temperature reached. The developed model and obtained results contribute to furthering the understanding of the electroporation process, and can be used for optimisation of the PEF process and its practical applications.
 

modelling,temperature,biological cell,membrane,pulsed electric field