Irreversible electroporation (IRE) is a less invasive therapy to ablate tumor cells by delivering short intensive electric pulses more than a few kV via needle-like electrodes. For reducing the required voltage for the IRE, a durable comb-shaped miniature electrode was designed to use in contact with the lesion surface for a new method named contact IRE. Methods: A miniature electrode was newly fabricated by a fine inkjet patterning and the subsequent etching of a copper-clad polyimide film. A train of 10-μs or 100-μs long electric pulses were applied 90 times at the interval of 1 s to a tissue phantom, and its cross section was observed to measure the necrotized area. Results: Cell experiments showed that the maximum ablation depth increased as a function of the applied voltage and reached 400 μm at 20 V. Furthermore, insulation of the lateral space between electrode teeth with a resin and administration of adjuvants to reduce the IRE threshold of the cell membrane did increase the ablation depth by 26% and the ablation area by 40%. Conclusion: The miniature electrode developed in this study successfully necrotized cells in a tissue phantom 400 μm deep from the surface with the electric pulses of only 20 V. Significance: The contact IRE for the surface of skin and gastrointestinal tract will ablate cutaneous and subcutaneous tumors by applying only several tens of volts.
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