Real-time impedance feedback to enhance cutaneous gene electrotransfer in a murine skin model

Electric field mediated gene delivery methods have the ability to efficiently transfect cells in vivo with an excellent safety profile. The method has historically used a fixed number of electric pulses with identical characteristics in induce delivery. Electrical treatment does not typically compensate for subject-to-subject variation and other differences. This study was designed to investigate if delivery/expression could be increased using a novel electropulsation method that compensated for variation using real-time electrical impedance measurements. The method involved delivering plasmid DNA encoding luciferase to murine skin. Tissue impedance in a 1-3 KHz range was measured before electric pulses were applied. Impedance was also measured after each successive pulse. Pulsation was stopped when impedance values were reduced by either 80% or 95% relative to prepulse values. Standard/fixed pulsing parameters were also used for comparison. The results indicated that up to 15-fold increases in luciferase expression could be obtained when electrical treatment was ceased based upon impedance reductions. Furthermore, peak expression levels of all treatment groups pulsed using the novel pulsing method were statistically higher than those that employed standard pulsing. These results strongly suggest that applying pulses until a defined impedance-based endpoint results in higher expression.