Testing electrode suitability for field stimulation of high-threshold biological preparations

Abstract

Introduction: A problem posed by electrical field (E) stimulation of biological preparations with high excitation threshold is that the E intensity required for excitation is likely to induce water electrolysis at the electrode surface, which can alter the extracellular medium and cause deleterious effects on the cells. In this study, different electrode materials and geometries were tested aiming at identifying electrode configurations that could transduce the E intensity required for exciting ventricular cardiomyocytes isolated from neonatal rats (threshold E ~30 V/cm) without causing water electrolysis. Methods: Wire and plate electrodes made of platinum, stainless steel and nickel/chrome alloy were used. The effect of blasting the electrode surface with sand and NaHCO 3 solution was also tested. Electrodes were inserted into a cell perfusion chamber containing the saline solution routinely used for physiological experiments. During E application for 5 min, the electrode surface and its surroundings were examined at high magnification for the presence of microbubbles, which indicates the occurrence of water electrolysis. The greatest E intensity applied that failed to generate microbubbles (E n ) was estimated. Results: While nickel/chrome and stainless steel electrodes resulted in low E n values, the best performance was observed for sandblasted platinum wire (2 mm diameter) and plate (25 mm x 5 mm; 0.1 mm thickness) electrodes, for which E n was ≥40 V/cm. Conclusion: These electrode configurations are suitable for effective and safe stimulation of isolated neonatal cardiomyocytes.

Tissue Engineering Techniques for Induced Pluripotent Stem Cell Derived Three-Dimensional Cardiac Constructs

“…Generally, electrical pacing for tissue engineering is performed by inserting an inert electrode composed of graphite or platinum into the media on either side of a tissue construct and by allowing a pulse of electrical current to pass through the tissue for a known duration (pulse width) and a known period between pulses (pulse frequency). 185 , 186 The pulse generates an electric field that replicates the electrical field caused by ion movement during an action potential. 187 Another method for electrical stimulation is the use of a salt bridge, which is the same concept but with a wet sponge separating the electrode from the target tissue.…”