Electroporation

Overview

Electroporation is a technique that takes advantage of the semi-permeable nature of cell membranes, a benefit of the presence of a phospholipid bilayer. When a suspension of cells mixed with foreign genetic material is exposed to the optimal ranges of electrical activity, regions in the phospholipid bilayer exhibit short-term disruptions, termed pores.  It is through these temporary pores (holes) that exogenous DNA, RNA or proteins can gain entry in the cell.

The process of electroporation consists of a voltage discharge transferred through the liquid of a cell in a pulse lasting a few microseconds. The electric pulse disrupts the phospholipid bilayer of the membrane and causes the formation of aqueous pores in the cells membrane.  The electric potential across the membrane of the cell rises by about 0.5-1.0 V, so that charged molecules (such as RNA or DNA) are driven across the membrane and through the pores.

Electroporation is a commonly used transfection and transformation technique in cell and molecular biology.  Scientists use special equipment such as electroporators, cuvettes and pipectrodes (i.e. The Cloning Gun) to conduct electroporation experiments.  Electroporators come in different shapes and sizes, from table top machines to handheld devices.

Electroporation Aftereffects

Electroporated cells are extremely fragile following treatment.  Once the pores are formed, scientists do not have control over what goes in and out of the cell.  As a result, some cells may die or malfunction due to this undesirable exchange of material.  Slight variations from the optimized conditions of the strength of electrical voltage may prevent cells from healing back to normal.  Instead, they may show permanent ruptures in the cell membrane and lead to cell death or toxicity.

After applying the electrical voltage, leaving the setup undisturbed allows the phospholipid bilayer to rearrange. During this time, the temporary pores may seal together (reversible electroporation) or enlarge, thus, rupturing the cell membrane (irreversible electroporation).  Reagents called electroporation buffers, which are formulations that mimic the cellular cytoplasm composition and enhance electroporation pore resealing, allow the electroporated cell membranes to heal and increase cell viability.

Applications

The insertion of exogenous DNA into cells is crucial for both expressing new genes and silencing existing genes using RNA interference or gene silencing.  Electroporation can be up to ten times as efficient as chemical reagents, does not require specific chemical reagents, and can be used in vivo.  Electroporation is extremely useful for difficult-to-transfect cell lines and primary cell transfection.  Widely used in gene therapy, cancer treatment, fusing cells together, transferring plasmids directly from one cell to another, and producing gene knockout systems (RNAi), electroporation is an incredibly valuable technique. There are even several commercially available electroporation kits that can help achieve high transfection efficiency and decrease cytotoxicity without extensive optimization of experimental parameters.

Scientists conducting experiments in Sus scrufa observed that the use of high voltage during electroporation precisely kills target cells without having any impact on surrounding tissues.  Further developments point to treatment of diseases requiring accurate tissue excision.  When used for cancer treatment it is referred to as cancer tumor electrochemotherapy.  Some companies have claimed to develop effective electroporation devices for removal of tumors.  Another significant application of electroporation is the delivery of DNA vaccines.  DNA vaccines, although still in the experimental phase, are considered a more direct and effective method than conventional cancer therapy.

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