One of current applications of electroporation is electrochemotherapy and electroablation for local cancer treatment. Both of these electroporation modalities share some similarities with radiation therapy, one of which could be the bystander effect. In this study, we aimed to investigate the role of the bystander effect following these electroporation-based treatments. During direct CHO-K1 cell treatment, cells were electroporated using one 100 µs duration square wave electric pulse at 1400 V/cm (for bleomycin electrotransfer) or 2800 V/cm (for irreversible electroporation). To evaluate the bystander effect, the medium was taken from directly treated cells after 24 h incubation and applied on unaffected cells. Six days after the treatment, cell viability and colony sizes were evaluated using the cell colony formation assay. The results showed that the bystander effect after bleomycin electrotransfer had a strong negative impact on cell viability and cell colony size, which decreased to 2.8% and 23.1%, respectively. On the contrary, irreversible electroporation induced a strong positive bystander effect on cell viability, which increased to 149.3%. In conclusion, the results presented may serve as a platform for further analysis of the bystander effect after electroporation-based therapies and may ultimately lead to refined application of these therapies in clinics.
Electroporation-based antitumor therapies, including bleomycin electrotransfer, calcium electroporation, and irreversible electroporation, are very effective on directly treated tumors, but have no or low effect on distal nodules. In this study, we aimed to investigate the abscopal effect following calcium electroporation and bleomycin electrotransfer and to find out the effect of the increase of IL-2 serum concentration by muscle transfection. The bystander effect was analyzed in in vitro studies on 4T1tumor cells, while abscopal effect was investigated in an in vivo setting using Balb/c mice bearing 4T1 tumors. ELISA was used to monitor IL-2 serum concentration. We showed that, similarly to cell treatment with bleomycin electrotransfer, the bystander effect occurs also following calcium electroporation and that these effects can be combined. Combination of these treatments also resulted in the enhancement of the abscopal effect in vivo. Since these treatments resulted in an increase of IL-2 serum concentration only in mice bearing one but not two tumors, we increased IL-2 serum concentration by muscle transfection. Although this did not enhance the abscopal effect of combined tumor treatment using calcium electroporation and bleomycin electrotransfer, boosting of IL-2 serum concentration had a significant inhibitory effect on directly treated tumors.
Coliform bacteria usually originate from the intestine, and the contamination typically occurs when there is a lack of sterility in food industry. PEF-induced selective nonthermal pasteurisation method might pasteurise coliform bacteria while leaving the needed bacteria intact. To evaluate this hypothesis, we chose Escherichia coli dh5α (E. coli) strain as a representation of coliform bacteria for this study. We also used Streptococcus thermophilus bacteria strain as a representation of lactobacteria used in milk by-products. The obtained results of PEF application showed that selective death of bacteria after PEF treatment can be induced. PEF was applied on bacteria. Then the clonogenic assay, the metabolic activity, and bacterial growth in the bioreactor were evaluated. By applying PEF treatment on E. coli and S. thermophilus their survival was monitored. We found the PEF parameters under which coliform bacteria E. coli were killed more than 100 times effectively than S. thermophilus. We postulate that it is the result of the bacteria size. Here we show that a PEF-induced selective nonthermal pasteurisation method could be applied in the industry where coliform bacteria can be eliminated while leaving other needed bacteria intact. We showed this by measuring the metabolic activity, the ability to form colonies, and the change in bacteria growth rate in the bioreactor.
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