Effects of electric pulse strength and pulse duration on plasmid DNA electromobility

Interstitial transport of DNA is a rate-limiting step in electric field-mediated gene delivery. Interstitial transport of macromolecules such as plasmid DNA is limited by small diffusion coefficient, large diffusion distance and inadequate convection. Here, we explore electric field as a novel interstitial driving force for plasmid DNA transport. We measured the electrophoretic movement, and hence, electromobility of fluorescently-labeled plasmid DNA in agarose gels of three concentrations (1, 2, and 3%), subjected to electric pulses at three levels of field strength (100, 200 and 400 V/cm) and four levels of pulse duration (10, 50, 75, 99 ms). In our experiments, electrophoresis is up to four orders of magnitude greater than diffusion for plasmid transport in agarose gel. In all gels, we found that shorter duration pulses (<10 ms) are not as efficient as longer duration pulses for pushing DNA. We also found that electromobility increases monotonically with applied voltage resulting in a maximum value at the highest applied voltage (400 V/cm) in all three gels. The rate of electromobility increase with applied voltage was amplified at higher gel concentration. These results indicate that plasmid DNA electromobility in porous media can be optimized through pulse duration and pulse strength.