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31.
Electroporation in dense cell suspension--theoretical and experimental analysis of ion diffusion and cell permeabilization 总被引:1,自引:0,他引:1
Electroporation is a process where increased permeability of cells exposed to an electric field is observed. It is used in many biomedical applications including electrogene transfection and electrochemotherapy. Although the increased permeability of the membrane is believed to be the result of pores due to an induced transmembrane voltage U(m), the exact molecular mechanisms are not fully explained. In this study we analyze transient conductivity changes during the electric pulses and increased membrane permeability for ions and molecules after the pulses in order to determine which parameters affect stabilization of pores, and to analyze the relation between transient pores and long-lived transport pores. By quantifying ion diffusion, fraction of transport pores f(per) was obtained. A simple model, which assumes a quadratic dependence of f(per) on E in the area where U(m)>U(c) very accurately describes experimental values, suggesting that f(per) increases with higher electric field due to larger permeabilized area and due to higher energy available for pore formation. The fraction of transport pores increases also with the number of pulses N, which suggest that each pulse contributes to formation of more and/or larger stable transport pores, whereas the number of transient pores does not depend on N. 相似文献
32.
Liévin Daugimont Nolwenn Baron Gaëlle Vandermeulen Natasa Pavselj Damijan Miklavcic Marie-Caroline Jullien Gonzalo Cabodevila Lluis M. Mir Véronique Préat 《The Journal of membrane biology》2010,236(1):117-125
The association of microneedles with electric pulses causing electroporation could result in an efficient and less painful
delivery of drugs and DNA into the skin. Hollow conductive microneedles were used for (1) needle-free intradermal injection
and (2) electric pulse application in order to achieve electric field in the superficial layers of the skin sufficient for
electroporation. Microneedle array was used in combination with a vibratory inserter to disrupt the stratum corneum, thus
piercing the skin. Effective injection of proteins into the skin was achieved, resulting in an immune response directed to
the model antigen ovalbumin. However, when used both as microneedles to inject and as electrodes to apply the electric pulses,
the setup showed several limitations for DNA electrotransfer. This could be due to the distribution of the electric field
in the skin as shown by numerical calculations and/or the low dose of DNA injected. Further investigation of these parameters
is needed in order to optimize minimally invasive DNA electrotransfer in the skin. 相似文献
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34.
Background
Electrochemotherapy and gene electrotransfer are novel promising treatments employing locally applied high electric pulses to introduce chemotherapeutic drugs into tumor cells or genes into target cells based on the cell membrane electroporation. The main focus of this paper was to calculate analytically and numerically local electric field distribution inside the treated tissue in two dimensional (2D) models for different plate and needle electrode configurations and to compare the local electric field distribution to parameter U/d, which is widely used in electrochemotherapy and gene electrotransfer studies. We demonstrate the importance of evaluating the local electric field distribution in electrochemotherapy and gene electrotransfer. 相似文献35.
Electroporation is the phenomenon that occurs when a cell is exposed to a high electric field, which causes transient cell membrane permeabilization. A paramount electroporation-based application is electrochemotherapy, which is performed by delivering high-voltage electric pulses that enable the chemotherapeutic drug to more effectively destroy the tumor cells. Electrochemotherapy can be used for treating deep-seated metastases (e.g. in the liver, bone, brain, soft tissue) using variable-geometry long-needle electrodes. To treat deep-seated tumors, patient-specific treatment planning of the electroporation-based treatment is required. Treatment planning is based on generating a 3D model of the organ and target tissue subject to electroporation (i.e. tumor nodules). The generation of the 3D model is done by segmentation algorithms. We implemented and evaluated three automatic liver segmentation algorithms: region growing, adaptive threshold, and active contours (snakes). The algorithms were optimized using a seven-case dataset manually segmented by the radiologist as a training set, and finally validated using an additional four-case dataset that was previously not included in the optimization dataset. The presented results demonstrate that patient''s medical images that were not included in the training set can be successfully segmented using our three algorithms. Besides electroporation-based treatments, these algorithms can be used in applications where automatic liver segmentation is required. 相似文献
36.
Andraž Polak Daniel Bonhenry François Dehez Peter Kramar Damijan Miklavčič Mounir Tarek 《The Journal of membrane biology》2013,246(11):843-850
Electroporation relates to the cascade of events that follows the application of high electric fields and that leads to cell membrane permeabilization. Despite a wide range of applications, little is known about the electroporation threshold, which varies with membrane lipid composition. Here, using molecular dynamics simulations, we studied the response of dipalmitoyl-phosphatidylcholine, diphytanoyl-phosphocholine-ester and diphytanoyl-phosphocholine-ether lipid bilayers to an applied electric field. Comparing between lipids with acyl chains and methyl branched chains and between lipids with ether and ester linkages, which change drastically the membrane dipole potential, we found that in both cases the electroporation threshold differed substantially. We show, for the first time, that the electroporation threshold of a lipid bilayer depends not only on the “electrical” properties of the membrane, i.e., its dipole potential, but also on the properties of its component hydrophobic tails. 相似文献
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38.
We demonstrate here that distribution of caspase-9 influences the pathway of apoptosis triggering, since caspase-9 is activated
efficiently only when it is distributed solely in the cytosol. Caspase-9 moves to the nuclei in a response to cell stress
during isolation of primary hepatocytes; this is called preapoptotic cell stress response. The dimethyl sulfoxide (DMSO) treatment
cannot prevent the migration of caspase-9 into the nuclei when it is added to primary hepatocytes immediately after isolation;
however, it can trigger redistribution of caspase-9 from the nuclei into the cytosol when added 1 day post-isolation. This
redistribution is temporary, since caspase-9 returns to the nuclei within 48 hours of DMSO treatment. Thereafter, some caspase-9
is retained in the nuclei of DMSO-treated hepatocytes for longer than in the nuclei of untreated hepatocytes. By measuring
caspase activities, we demonstrate that the addition of DMSO to cell culture medium can temporarily normalize the susceptibility
of hepatocytes for apoptosis triggering through the intrinsic pathway. DMSO contributes also to the prolonged pathway inactivation,
i.e., by extending preapoptotic cell stress response. We propose that DMSO extends the survival of primary hepatocytes by
modulating preapoptotic cell stress response, which could be exploited for extending the lifespan of other primary cell cultures. 相似文献
39.
During the electroporation cell membrane undergoes structural changes, which increase the membrane conductivity and consequently lead to a change in effective conductivity of a cell suspension. To correlate microscopic membrane changes to macroscopic changes in conductivity of a suspension, we analyzed the effective conductivity theoretically, using two different approaches: numerically, using the finite elements method; and analytically, by using the equivalence principle. We derived the equation, which connects membrane conductivity with effective conductivity of the cell suspension. The changes in effective conductivity were analyzed for different parameters: cell volume fraction, membrane and medium conductivity, critical transmembrane potential, and cell orientation. In our analysis we used a tensor form of the effective conductivity, thus taking into account the anisotropic nature of the cell electropermeabilization and rotation of the cells. To determine the effect of cell rotation, as questioned by some authors, the difference between conductivity of a cell suspension with normally distributed orientations and parallel orientation was also calculated, and determined to be <10%. The presented theory provides a theoretical basis for the analysis of measurements of the effective conductivity during electroporation. 相似文献
40.
This paper investigates the influence of cell density on cell membrane electropermeabilization. The experiments were performed
on dense cell suspensions (up to 400 × 106 cells/ml), which represent a simple model for studying electropermeabilization of tissues. Permeabilization was assayed with
a fluorescence test using Propidium iodide to obtain the mean number of permeabilized cells (i.e. fluorescence positive) and
the mean fluorescence per cell (amount of loaded dye). In our study, as the cell density increased from 10 × 106 to 400 × 106 cells/ml, the fraction of permeabilized cells decreased by approximately 50%. We attributed this to the changes in the local
electric field, which led to a decrease in the amplitude of the induced transmembrane voltage. To obtain the same fraction
of cell permeabilization in suspensions with 10 × 106 and 400 × 106 cells/ml, the latter suspension had to be permeabilized with higher pulse amplitude, which is in qualitative agreement with
numerical computations. The electroloading of the cells also decreased with cell density. The decrease was considerably larger
than expected from the differences in the permeabilized cell fractions alone. The additional decrease in fluorescence was
mainly due to cell swelling after permeabilization, which reduced extracellular dye availability to the permeabilized membrane
and hindered the dye diffusion into the cells. We also observed that resealing of cells appeared to be slower in dense suspensions,
which can be attributed to cell swelling resulting from electropermeabilization. 相似文献