Fabrication of Nano- and Micro-Structured PPy Electrode and its Application to Electroporation to Cell

Abstract

Electroporation using microstructured electrodes, which generate a localized high electric field, allows molecules (genes) to be introduced into cells; however, there are some technical issues with the fabrication process and material in terms of cytotoxicity and cost. In this study, polypyrrole (PPy), a biocompatible and conductive polymer, is nano- and micro-structured for an electrode of electroporation by electrochemical polymerization. Nano- and micro-scale dots of PPy are generated by a specific pulse waveform of applied voltage in a considerably low concentration of pyrrole (monomer) solution. The conductivity of PPy is changed from 4 to 16 S/cm by dopant concentration with a range of 0.025 M to 0.2 M. It is demonstrated that electroporation using the PPy and ITO electrodes introduce test agent of molecules (Propidium Iodide) into HeLa cells, where 10 and 50 V of pulse voltage is applied. The electroporation using nano-scale dots of PPy electrodes provides a 40% higher introduction rate than that of the micro-dots of PPy electrodes. The introduction rate in electroporation using the nano-scale dots of PPy can be maintained above 95% regardless of the application time of voltage, whereas that of the micro-scale dots of PPy electrodes increases with the application time. It is reasonable to assume that the nano- and micro-structured PPy electrodes are effective in electroporation, as the introduction rates on these PPy electrodes are higher than that of the ITO electrode. However, the cell viability in the electroporation using the nano-scale of PPy electrodes decreases by approximately 30% with application time. Both the introduction rate and cell viability slightly decrease with the conductivity of the PPy electrode; therefore, they are dominated by surface morphologies of the PPy electrode and applied voltage as compared to that of electrode conductivity. Nevertheless, it is demonstrated that the nano- and micro-structured PPy electrodes improve the efficiency of electroporation owing to the locally concentrated electric field.