An experimentally validated numerical model of pH changes in surrogate tissue induced by electroporation pulses

Electroporation often leads to electrochemical reactions at the electrode-electrolytic solution interface, particularly when using monophasic pulses of considerable duration (typically on the order of several microseconds or longer) that cause not only capacitive charging of the double-layer, but also faradaic charge transfer between the electrodes and the solution. Applications, where the electrochemical changes are to be either avoided or actively exploited to benefit the treatment, range from gene electrotransfer to electrolytic ablation of tissue. Through numerical modelling and experimental validation, our study explores the extent of pH changes induced by faradaic currents in a surrogate tissue. A mechanistic multiphysics model of pH changes was developed based on first principles, incorporating hydrolysis reactions at the anode and cathode, and the Nernst-Planck model of ion transport. The model was validated using agarose gel tissue phantoms designed to simulate unbuffered and buffered (mimicking in vivo tissue buffering capacity) conditions. An imaging system with pH-sensitive dyes was developed and used to visualise and quantify pH front formation and migration. The model predictions qualitatively aligned well with experimental data, differentiating pH front behaviour between unbuffered and buffered media. However, the quantitative accuracy in predicting the temporal and spatial evolution of the pH fronts can be further improved. Experimental observations emphasise the need for more advanced models. Nevertheless, the developed model provides a sound theoretical foundation for predicting pH changes due to high-voltage electric pulse delivery, such as encountered in electroporation-based treatments and therapies.