Fig. 3

Effect of different pulsing protocols on gene electrotransfer efficiency (percentage of transfected cells) in a 3D collagen model with embedded CHO cells, pDNA was administrated on top of the gel. A Different combinations of high-voltage (HV) and low-voltage (LV) pulses were applied. The electric pulse parameters were as follows: HV 1 (5 × 1 ms; 0.8 kV/cm; 1 Hz), HV 2 (8 × 200 µs; 0.8 kV/cm; 1 Hz), LV 1 (1 × 100 ms; 75 V/cm) and LV 2 (1 × 100 ms; 150 V/cm). The time lag between HV and LV pulse was 20 ms. B 8 × 1 ms pulses (1 Hz) and E = 0.8 kV/cm with single polarity (SP) or orthogonal both polarities (OBP) were applied; cells were embedded in collagen gel (3D model). pDNA concentration in electroporation media was 90 μg/ml. Values represent means (all tests were performed in triplicate) and error bars are determined from standard deviation. Results were considered as statistically different when p < 0.05