For some time now our lab has used the Bio-Rad Gene Pulser II System for the efficient electroporation of eukaryotic and prokaryotic cells. The electroporation method for transforming cells is based on the permeabilization of the cell membranes via stimulation with an electric pulse. We primarily use the Gene Pulser II System to transform electrocompetent bacterial cells, such as DH5alpha or MC1061, and have had good results. We generally use a high voltage, low capacitance setting to ensure efficient transformation.
The Gene Pulser II System consists of 3 components: i) the main Gene Pulser II unit, which uses a proprietary Pulse Trac waveform delivery system that, according to Bio-Rad, generates the most accurate exponential decay pulses possible, ii) the Pulse Controller PLUS, which increases the effective DNA delivery into cells by increasing the control of the high voltage pulses and iii) the Capacitance Extender PLUS, which provides a wide range of precision capacitors for reproducible time constants. The Gene Pulser II System delivers the pulse rapidly from the selected capacitor. The field strength (kV/cm), which is determined by the voltage setting, and the time constant (tau), time required for initial voltage (Vo) to decay to 34% of Vo which is determined by the resistance and capacitance, are used to describe the pulse that is delivered. After a successful pulse delivery an indicator tone is produced both the time constant and peak voltage are accurately measured and displayed on the LED of the main unit.
The Gene Pulser II System also has some nice safety features built in. For instance, when a high voltage pulse delivery is interrupted, the voltage is diverted to ground, avoiding a dangerous discharge. We also appreciate the fact that we have access to various methods and references for the electroporation of different cell types online. We have used some of these methods and have found them to work just as described. The few problems that we have had with this system are mainly problems associated with the cuvettes. For instance, we have noticed that carbon deposits build up on the electrode contacts in the shocking chamber and cleaning of this area is needed on a regular basis. Also, it can sometimes be difficult to get firm contact between the cuvette in the cuvette slide and the electrodes. We commonly use the Pulse Controller at a setting of 2.5 kV, but the unit can only be adjusted by 10 V increments, which makes setting the unit slow and tedious. Finally, it’s important to be aware that when handling the cuvettes it is important to be wearing gloves. In our experience, if the cuvettes are handled with bare hands, salts or oils (or both) are deposited onto them, which increases the chances of arcing.
Overall we have found the Gene Pulser II System to be a reliable system for electroporation. We use this machine on a regular basis and have been pleased with the results.
Hee Chul Lee
Graduate Student
Dept. of Biochemistry
NYU School of Medicine