Optimum Conductivity of Gels for Electric Field Homogenization in Tissue Electroporation Therapies

Abstract

Electroporation is used in tissue for gene therapy, drug therapy and minimally invasive tissue ablation. For the electroporation to be successful, the electrical field that develops during the application of the pulses needs to be precisely controlled. It is desirable to generate a homogeneous electric field in the region of interest and a null electric field in the regions not to be treated. In case of irregularly shaped tissue structures, such as bulky tumors, electric field homogeneity is almost impossible to be achieved with current electrode arrangements. In the past (Bioelectrochemistry, 70:2, 551–60, 2007), we proposed the use of conductive gels, matched to the conductivity of the tissues, to overcome this limitation. Those gels can be used to fill the dead spaces between plate electrodes gripping the tissue so that the electric field distribution becomes homogeneous. Here we analyze, through finite element simulations, how relevant the conductivity mismatches are. We found that conductivity mismatching errors are surprisingly well tolerated by the technique and that it is more convenient to use gels with higher conductivity than the conductivity of tissues rather than gels with lower conductivity. A gel with a conductivity of 5 mS/cm could be a proper solution for most cases.