Knowledge of the parameters which influence the efficiency of gene electrotransfer has importance for practical implementation of electrotransfection for gene therapy as well as for better understanding of the underlying mechanism. The focus of this study was to analyze the differences in gene electrotransfer and membrane electropermeabilization between plated cells and cells in a suspension in two different cell lines (CHO and B16F1). Furthermore, we determined the viability and critical induced transmembrane voltage (ITV(c)) for both cell lines. In plated cells we obtained relatively little difference in electropermeabilization and gene electrotransfection between CHO and B16F1 cells. However, significant differences between the two cell lines were observed in a suspension. CHO cells exhibited a much higher gene electrotransfection rate compared to B16F1 cells, whereas B16F1 cells reached maximum electropermeabilization at lower electric fields than CHO cells. Both in a suspension and on plated cells, CHO cells had a slightly better survival rate at higher electric fields than B16F1 cells. Calculation of ITV(c) in a suspension showed that, for both electropermeabilization and gene electrotransfection, CHO cells have lower ITV(c) than B16F1 cells. In all cases, ITV(c) for electropermeabilization was lower than ITV(c) for gene electrotransfer, which is in agreement with other studies. Our results show that there is a marked difference in the efficiency of gene electrotransfer between suspended and plated cells.

In this study, we compared three different methods used for quantification of gene electrotransfer efficiency: fluorescence microscopy, flow cytometry and spectrofluorometry. We used CHO and B16 cells in a suspension and plasmid coding for GFP. The aim of this study was to compare and analyse the results obtained by fluorescence microscopy, flow cytometry and spectrofluorometry and in addition to analyse the applicability of spectrofluorometry for quantifying gene electrotransfer on cells in a suspension. Our results show that all the three methods detected similar critical electric field strength, around 0.55 kV/cm for both cell lines. Moreover, results obtained on CHO cells showed that the total fluorescence intensity and percentage of transfection exhibit similar increase in response to increase electric field strength for all the three methods. For B16 cells, there was a good correlation at low electric field strengths, but at high field strengths, flow cytometer results deviated from results obtained by fluorescence microscope and spectrofluorometer. Our study showed that all the three methods detected similar critical electric field strengths and high correlations of results were obtained except for B16 cells at high electric field strengths. The results also demonstrated that flow cytometry measures higher values of percentage transfection compared to microscopy. Furthermore, we have demonstrated that spectrofluorometry can be used as a simple and consistent method to determine gene electrotransfer efficiency on cells in a suspension.

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BackgroundIn the context of spore contamination involved in bio-terrorism and food preservation, the development of new techniques for spore inactivation is an important challenge.ResultsHere, a successful application of electric arc discharges resulting in spore death was reported. Two types of electric arcs were compared, different with respect to their durations. The discharges with 0.5 μs duration induced a small inactivation area of 0.6 % of surface treated around their point of entry into the sample, while those with 20 μs duration induced a much larger inactivation area from 7 to 55 % of surface treated roughly proportional to the number of discharges delivered. In particular, 50 discharges of 20 μs duration induced inactivation in more than 55% of surface treated at an inactivation rate above 3.6 log10.ConclusionsThese results are promising and warrant developing electric arcing as a novel method for spore inactivation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-016-0764-x) contains supplementary material, which is available to authorized users.

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