Electrode Corrosion in Electrochemotherapy Can Hinder Treatment Efficacy

Abstract

Introduction:

Electrochemotherapy is an established treatment for primary and secondary cutaneous tumors of various histologies, combining chemotherapy with the delivery of high-voltage electric pulses to enhance drug uptake. Electric pulses induce water electrolysis, leading to extreme pH changes around the electrodes—acid at the anode and base at the cathode—causing tissue damage and contributing to a self-sterilizing effect, but also promoting needle corrosion. These pH shifts depend on pulse parameters, electrode geometry, and the surrounding medium; although natural tissue buffers can mitigate them, neutralization is often incomplete. This work analyzes the effect of pH changes on needle deterioration during pulse delivery.

Materials and Methods:

Needle electrodes were inserted into an ex vivo tissue model and subjected to eight 100 µs monopolar pulses of 1,000 V/cm at 5,000 Hz. Every 50 trains, electrodes were inserted into a gel with a pH indicator, and a single pulse was delivered to visualize nonconducting areas. Electrode surfaces were photographed, and COMSOL simulations analyzed electric field variations due to isolated regions. Electrodes were then sanded to assess if removing corrosion restored conductivity. In addition, a buffered gel was developed to reduce corrosion.

Results:

New needles showed significant conductivity loss after 50 trains and were almost completely isolated after 150 trains. While this suffices for treating most tumors, extensive treatments requiring over 300 trains demand electrode replacement before reaching 150 trains. Sanding temporarily restores conductivity, but sanded electrodes corrode more rapidly, losing effectiveness after fewer than 50 additional trains. A specifically designed buffered gel improved electrode durability by maintaining conductivity and could help minimize skin side effects.