Electroporation mechanism

Weaver, J.C., Barnett, A., 1992. Guide to Electroporation and Electrofusion in Progress toward a Theoretical Model of Electroporation Mechanism Membrane Electrical Behavior and Molecular Transport, 26. 

Transfection is the process of introducing DNA or RNA into eukaryotic ceils. The use of transfection is to study the role and regulation of proteins or to understand the mechanisms of a pathway. Transfection can be transient for rapid analysis or stable , mostly for induction of expression. There are various methods of transfection which include electroporation, viral vectors, DEAE-Dextran, calcium phosphate or Lipofectamine. The choice of transfection depends on the cell type used. The most desirable technique is the one which gives high efficiency of nucleic acid transfection with less interference to the cells physiology and high reproducibility. 

The mechanism by which electroporation enhances i.m. pDNA expression and efficacy requires further study. For muscle transfection, it has been demonstrated that electroporation appears to increase the number of muscle fibers transfected by as much as ten-fold (Dupuis et al., 2000). In addition, the number of muscle nuclei containing transfected pDNA is higher after electroporation. The mechanism by which electroporation enhances transfection of tumor tissue is unclear at this time. 

Although it is generally believed that electroporation involves the creation of aqueous pathways (pores) in the stratum corneum [24], this mechanism remains somewhat controversial. These proposed channels have not yet been identified in any microscopic study due to their small size (about 10 nm), sparse distribution (<0.1% of the total skin area), and shortlived nature (millisecond to second) [16,25]. 

Iontophoresis by definition is the process of transport of ions into or through a tissue by the use of an applied potential difference across the tissue [52], Depending on the physicochemical characteristics of a molecular species, electrorepulsion is usually the primary mechanism of transdermal transport for ions, whereas electroosmosis and increased passive diffusion (as a result of the reduced barrier properties) are more prominent for neutral species [53]. In contrast, enhancement in flux for neutral or weakly charged species during electroporation arises predominantly from the reduced barrier properties of the membrane, whereas direct electrorepulsion is usually of secondary importance [25],... 

As the mechanisms of penetration and acceleration during iontophoresis or electroporation are different, the application of a constant direct current after pulsing may raise penetration even further in comparison with either method alone. Table 15.2 shows that for L-glutamic... 

Prausnitz, M.R., et al. 1993. Electroporation of mammalian skin A mechanism to enhance transdermal drug delivery. Proc Natl Acad Sci USA 90 10504. 

Tokudome, Y., and K. Sugibayashi. 2004. Mechanism of the synergic effects of calcium chloride and electroporation on the in vitro enhanced skin permeation of drugs. J Control Release 95 (2) 267. 

Cell lysis Mechanical methods pressure shearing, ultrasonic disintegration, bead-mill homogenizers Nonmechanical methods enzymatic lysis, osmotic lysis, freezing and thawing, detergent-based lysis and electroporation... 

FIGURE 8.41 Illustrations of experimental setup and mechanism of the electroporation chip (a) DNA attraction and targeting and (b) electroporation processes [370]. Reprinted with permission from the Royal Society of Chemistry. 

Although the mechanisms of electroporation, electrofusion, and electroinsertion are not known, biophysical data suggest that the primary field pulse effect is interfacial polarization by ion accumulation at the membrane surfaces. The resulting transmembrane electric field causes rearrangements of the lipids such that pores are formed1718. Electropores anneal slowly (over a period of minutes) when the pulse is switched off. 

The continuous interest and growth of the various new industrial processes related to the life sciences will also require significant contributions from membrane engineering. It is hoped that future research would provide deeper insight on the precise mechanisms involved, which would show new direction for research in membrane science and applications. It is, however, important to recognize that applicability of electroporation has been demonstrated in a variety of bacteria, yeast, and mammalian cells and some applications are ready for exploitation while many new technologies seem potentially possible. 

Electroporated cells can be used to transfer DNA in bacterial, plant, and mammalian cells. This method offers rapid and efficient incorporation of plasmid and DNA in cells [49]. The in vivo electroporation has been shown to yield enhanced plasmid delivery to a wide range of tissues including muscle, skin, liver, lung, artery, kidney, retina, cornea, spinal cord, brain, synovium, and tumors. The precise mechanisms involved in electroporation applications in vivo are uncertain and require further studies, but appear to involve both electropore formation and an electrophoretic movement of the plasmid DNA. 

Mishra, K.P., Mechanisms of cell electroporation of human erythroc3fte for cell fusion hy centrifugation. Proceedings of National Symposium on New Methodologies, Indian Institute of Technology, Mumbai, March 7, 1990. 

The present summary will cover only those technologies where the drug formulation itself is used to penetrate the skin via its mechanical energy. It will not describe any technology where a needle is used to puncture the skin, even if the needle is not visible to the patient or only the epidermis is punctured, such as mini-needles, microneedles, pen injectors, or autoinjectors. Also excluded are systems that ablate the skin mechanically or otherwise disrupt its chemical or mechanical structure to increase its permeability, such as laser ablation, microdermal ablation, electroporation, or iontophoresis. These are usually referred to as transdermal drug delivery, but can also be described as needle free. 

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