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The use of high-frequency short bipolar pulses in cisplatin electrochemotherapy in vitro

Maria Scuderi
Maria Scuderi
, 
Matej Rebersek
Matej Rebersek
, 
Damijan Miklavcic
Damijan Miklavcic
 and 
Janja Dermol-Cerne
Janja Dermol-Cerne
   | Jun 01, 2019
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Article Category: Research Article
Published Online: Jun 01, 2019
Page range: 194 - 205
Received: Feb 04, 2019
Accepted: Apr 23, 2019
DOI: https://doi.org/10.2478/raon-2019-0025
© 2019 Maria Scuderi, Matej Rebersek, Damijan Miklavcic, Janja Dermol-Cerne, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Figure 1

Scheme of the applied pulses. (A) 100 μs long monopolar pulses of amplitude ΔU (80 V – 240 V in a step of 40 V) were applied with a repetition frequency of 1 Hz. (B) Short bipolar pulses (HF-EP). Above: 8 bursts were applied with a repetition frequency of 1 Hz. Down left: One burst was 200 μs long and consisted of 50 bipolar pulses. Below right: One bipolar pulse of amplitude ΔU (100 V – 1000 V in a step of 100 V) consisted of 1 μs long positive pulse, 1 μs long negative pulse (both of voltage ΔU) with a 1 μs long delay between pulses.
Scheme of the applied pulses. (A) 100 μs long monopolar pulses of amplitude ΔU (80 V – 240 V in a step of 40 V) were applied with a repetition frequency of 1 Hz. (B) Short bipolar pulses (HF-EP). Above: 8 bursts were applied with a repetition frequency of 1 Hz. Down left: One burst was 200 μs long and consisted of 50 bipolar pulses. Below right: One bipolar pulse of amplitude ΔU (100 V – 1000 V in a step of 100 V) consisted of 1 μs long positive pulse, 1 μs long negative pulse (both of voltage ΔU) with a 1 μs long delay between pulses.

Figure 2

Cell membrane permeability and cell survival as a function of electric field for (A) 8 x 100 μs long monopolar pulses, delivered at repetition frequency 1 Hz; (B) 8 bursts of short bipolar pulses (HF-EP) of 1-1-1-1 μs, delivered at repetition frequency 1 Hz. Each data point was repeated 3–4 times (mean ± standard deviation). In the control sample, no pulses were applied. Note different scales on the x-axes. On (A), the threshold of electroporation was at 0.8 kV/cm (P = 0.029, t-test) and survival did not decrease in comparison with control (one-sample t-test). On (B) the threshold of electroporation was at 2 kV/cm (P = 0.022, t-test), while the survival decreased at 4.5 kV/cm (P = 0.004, one-sample t-test). In Figure 2B, blue asterisks refer to permeability curve and red asterisks to the survival curve.
Cell membrane permeability and cell survival as a function of electric field for (A) 8 x 100 μs long monopolar pulses, delivered at repetition frequency 1 Hz; (B) 8 bursts of short bipolar pulses (HF-EP) of 1-1-1-1 μs, delivered at repetition frequency 1 Hz. Each data point was repeated 3–4 times (mean ± standard deviation). In the control sample, no pulses were applied. Note different scales on the x-axes. On (A), the threshold of electroporation was at 0.8 kV/cm (P = 0.029, t-test) and survival did not decrease in comparison with control (one-sample t-test). On (B) the threshold of electroporation was at 2 kV/cm (P = 0.022, t-test), while the survival decreased at 4.5 kV/cm (P = 0.004, one-sample t-test). In Figure 2B, blue asterisks refer to permeability curve and red asterisks to the survival curve.

Figure 3

Cell membrane permeability as a function of different time of propidium iodide administration after electroporation for (A) 8 x 100 μs long monopolar pulses, delivered at a repetition frequency 1 Hz; (B) 8 bursts of short bipolar pulses (HF-EP) of 1-1-1-1 μs, delivered at repetition frequency 1 Hz. Each data point was repeated 4 times (mean ± standard deviation). We performed a 1-way ANOVA on ranks. For both types of pulses, there was a significant difference between 0 min vs 10 min and 20 min (P < 0.05), other pairwise comparisons were not significant.
Cell membrane permeability as a function of different time of propidium iodide administration after electroporation for (A) 8 x 100 μs long monopolar pulses, delivered at a repetition frequency 1 Hz; (B) 8 bursts of short bipolar pulses (HF-EP) of 1-1-1-1 μs, delivered at repetition frequency 1 Hz. Each data point was repeated 4 times (mean ± standard deviation). We performed a 1-way ANOVA on ranks. For both types of pulses, there was a significant difference between 0 min vs 10 min and 20 min (P < 0.05), other pairwise comparisons were not significant.

Figure 4

Cytotoxicity of cisplatin without electroporation at different concentrations and time of incubation. Each data point was repeated 4 times (mean ± standard deviation) and is normalized to the control sample in which cisplatin was substituted by 0.9% NaCl. A 2-way ANOVA was performed. 10 min or 1 h of incubation was different from 24 h or 48 h (P < 0.001) while there was no difference between 10 min vs 1 h and 24 h vs 48 h. 330 μM cisplatin was more cytotoxic than other tested concentrations (P < 0.001). There was no significant difference between 1 μM and 10 μM cisplatin; all other comparisons were significantly different (P < 0.001).
Cytotoxicity of cisplatin without electroporation at different concentrations and time of incubation. Each data point was repeated 4 times (mean ± standard deviation) and is normalized to the control sample in which cisplatin was substituted by 0.9% NaCl. A 2-way ANOVA was performed. 10 min or 1 h of incubation was different from 24 h or 48 h (P < 0.001) while there was no difference between 10 min vs 1 h and 24 h vs 48 h. 330 μM cisplatin was more cytotoxic than other tested concentrations (P < 0.001). There was no significant difference between 1 μM and 10 μM cisplatin; all other comparisons were significantly different (P < 0.001).

Figure 5

Cytotoxicity of cisplatin in combination with electroporation (EP) at fixed value of cisplatin (CDDP) 100 μM as a function of electric field: (A) 8 x 100 μs long monopolar pulses (ECT) were delivered at repetition frequency 1 Hz; (B) 8 bursts of short bipolar pulses (HF-EP) of 1-1-1-1 μs were delivered at repetition frequency 1 Hz. Each data point was repeated 3–6 times (mean ± standard deviation). Results are normalized to the control sample without an electric field and with 100 μM cisplatin. We performed a (A) 2-way ANOVA or (B) 2-way ANOVA on ranks. (A) At 0.8 kV/cm (P = 0.036) and 1 kV/cm and 1.2 kV/cm (P < 0.001) EP samples were significantly different from CDDP+EP samples. (B) At electric fields equal to or higher than 2 kV/cm EP samples were significantly different from CDDP+EP samples (P < 0.001).
Cytotoxicity of cisplatin in combination with electroporation (EP) at fixed value of cisplatin (CDDP) 100 μM as a function of electric field: (A) 8 x 100 μs long monopolar pulses (ECT) were delivered at repetition frequency 1 Hz; (B) 8 bursts of short bipolar pulses (HF-EP) of 1-1-1-1 μs were delivered at repetition frequency 1 Hz. Each data point was repeated 3–6 times (mean ± standard deviation). Results are normalized to the control sample without an electric field and with 100 μM cisplatin. We performed a (A) 2-way ANOVA or (B) 2-way ANOVA on ranks. (A) At 0.8 kV/cm (P = 0.036) and 1 kV/cm and 1.2 kV/cm (P < 0.001) EP samples were significantly different from CDDP+EP samples. (B) At electric fields equal to or higher than 2 kV/cm EP samples were significantly different from CDDP+EP samples (P < 0.001).

Figure 6

Cytotoxicity of cisplatin at different concentration of cisplatin (CDDP) and electroporation (EP) at a fixed value of electric field (A) 1.2 kV/cm, 8x100 μs long monopolar pulses, delivered at repetition frequency 1 Hz; (B) 3 kV/cm, 8 bursts of short bipolar pulses (HF-EP) of 1-1-1-1 μs, delivered at repetition frequency 1 Hz. Each data point was repeated 3-7 times (mean ± standard deviation). Each data was normalized to the control sample electroporated and with 0.9% NaCl instead of cisplatin. We performed a 2-way ANOVA. For both types of pulses, at 100 μM and 330 μM the CDDP samples were significantly different from the CDDP+EP samples (P < 0.001).
Cytotoxicity of cisplatin at different concentration of cisplatin (CDDP) and electroporation (EP) at a fixed value of electric field (A) 1.2 kV/cm, 8x100 μs long monopolar pulses, delivered at repetition frequency 1 Hz; (B) 3 kV/cm, 8 bursts of short bipolar pulses (HF-EP) of 1-1-1-1 μs, delivered at repetition frequency 1 Hz. Each data point was repeated 3-7 times (mean ± standard deviation). Each data was normalized to the control sample electroporated and with 0.9% NaCl instead of cisplatin. We performed a 2-way ANOVA. For both types of pulses, at 100 μM and 330 μM the CDDP samples were significantly different from the CDDP+EP samples (P < 0.001).
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