Electrical resistance in inhomogeneous samples during electroporation

Abstract

In electrochemotherapy (ECT), electric field is applied by means of needle pairs to the tumor tissue in order to permeabilize cell membranes and, as a consequence, enhance the effects of chemotherapeutic drugs. The target tissue is not homogeneous and the electric field, generated by the needle pairs, is strongly affected by the specific electrical characteristics of different tissues. This paper analyzes the effect of tissue in homogeneity by means of numerical models and suitable experiments

Electric field distribution study in inhomogeneous biological tissues

“…In Equation , the conductivity, σ [S/m], could be constant or dependent on the electric field intensity, E [V/m]. In particular, a model to describe the variation of potato conductivity dependence on electric field intensity is where σ 0 and σ EP , in [S/m], are the conductivity measured for the nonelectroporated and electroporated tissues, respectively, and k v and E th are parameters obtained fitting the experimental data as in Campana et al and Dughiero et al E th in [V/cm] is the threshold of electric field intensity approximately close to the electroporation threshold, and k v in [cm/V] is a parameter that manages the transition from electroporated and not electroporated tissue that in Kavian et al was defined as “speed of the switch” not electroporated to electroporated tissue.…”

“…Gelatine (bought at local market), deionized water, agar (Meat Liver Agar Sigma‐Aldrich 46379), corn starch (bought at local market), glycerine, and sodium chloride (NaCl) were used as received. The list and amount of ingredients used for gel preparation is reported in Table …”

“…The procedure for the preparation of the TMM involves the following four steps: The glycerin is added to 20 mL of deionized water at room temperature, in a beaker; and then corn starch is slowly added while stirring vigorously. In a second beaker, the gelatin or agar is heated in a microwave oven at 90°C with 50 mL of deionized water and NaCl for 30 seconds, until the gelatin or agar is dissolved into a thick mixture. The viscous mixture from step (i) is added to the one obtained in step (ii). They are alternately stirred manually and heated in a microwave oven for 15 seconds, until the whole mixture turns semisolid. The semisolid material is cast into samples with suitable sizes for the experiments (Figure A). …”

“…The list and amount of ingredients used for gel preparation is reported in Table 1. 27,33 The procedure for the preparation of the TMM involves the following four steps 33 :…”

“…where σ 0 and σ EP , in [S/m], are the conductivity measured for the nonelectroporated and electroporated tissues, respectively, and k v and E th are parameters obtained fitting the experimental data as in Campana et al 33 and Dughiero et al 44 E th in [V/cm] is the threshold of electric field intensity approximately close to the electroporation threshold, 42,43 and k v in [cm/V] is a parameter that manages the transition from electroporated and not electroporated tissue that in Kavian et al 42 was defined as "speed of the switch" not electroporated to electroporated tissue. To obtain the electric field distributions and magnitudes as close to the real-world values, the simulations were performed using the experimentally obtained conductivity values for the potato, gel (at the center), and apple tissues.…”