Flow-type electroporation chips for gene transfection

Electroporation is a technique with which DNA molecules can be delivered into cells in a chamber using high electric field pulses. The limited amount of target cells and the potential risk from the high voltage are the two drawbacks in this technique. This study aimed to fabricate an electroporation chip to manage large amount of cells continuously with a lower applied voltage. The electroporation chip, consisting of a micro-channel with thin film electrodes made of gold or platinum wire electrodes on both sides, was fabricated on PMMA material using evaporation, photolithography, wet-etching, lift-off, and fusion-bonding methods. The suspension fluid of Huh-7 cell lines (1×10⁶ cells/ml) mixed with 10 μg plasmids equipped with lacZ genes in a volume of 500 μl flowed through the channel with a variety of flow rates under a series of square pulses with 1-10 ms in width and 10 Hz in frequency. Trypan-blue staining assessed the viability of the cells treated with pulses. The transfection rate was evaluated with blue-staining cells under X-Gal stain 24 hours later. The dimensions of the channel were 5 mm wide, 0.2 mm high, and 25 mm long. Two types of electrodes, parallel-plate type and parallel-line type electrodes, were fabricated and tested in these experiments. The fabricated microchip can deliver genes into the flowing cells. The electric pulse frequency that determines the shock number for each cell for a fixed flow rate can be optimized for better transfection and survival rates.