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Electroporation is a physical method that delivers plasmid DNA in a variety of tissues. This technology is currently gaining recognition and acceptance in the scientific community as evidenced by the number of studies using in vivo electroporation published each year. One potential application for this method is to deliver DNA to the cells that comprise tumors. [ABSTRACT FROM AUTHOR]

Of the many methods and techniques for in vivo gene transfer, some have already been used in clinical trials. In most cases, genes are transferred into tissues using the infectivity of viral particles. However, viral systems have some known drawbacks (1,2). If an efficient and specific transfer method could be developed, naked plasmid DNA would be an ideal system for gene transfer. Plasmid-mediated methods would be economical and easy. Also, the transfer procedure could be easily repeated, as naked plasmid DNA has little antigenicity for the host (3,4). [ABSTRACT FROM AUTHOR]

Administering a chemotherapeutic agent in combination with electric fields (electrochemotherapy; ECT) has been shown to be an effective localized treatment for solid tumors (1). The drug used most often in this combination treatment has been bleomycin. ECT has been used successfully in both animal studies and clinical trials (1-3). The treatment was initially performed by exposing tumor cells to electrical fields following intravenous injection of the chemotherapeutic agent. Although ECT using intravenous bleomycin was successful, the procedure was limited by the existence of a narrow but optimal time window for effective treatment as well as the fact that a systemic drug dose was being administered for a localized therapy. In addition, the use of intravenous administration also precludes the treatment of patients with poor circulation. [ABSTRACT FROM AUTHOR]

The skin is an especially attractive target for gene therapy. In particular, the ability to target genes to the epidermis of the skin could be used to correct skin-specific disorders as well as for the production of proteins secreted into the skin and the circulatory system to correct certain systemic diseases (1-3). For example, genes expressing cytokines, interferons, or other biologically active molecules could be used to treat skin tumors or other lesions. In addition, keratinocytes and fibroblasts in the skin may secrete protein factors to treat systemic conditions such as hemophilia (4). In other words, this technology for skin-targeted gene therapy would be useful not only for treating local indications, but also for treating systemic diseases by exploiting the secretory capability of the epidermal keratinocytes (5). It is reasonable to believe that skin-targeted gene delivery has great potential and is biologically sound as is indicated by the substantial in vitro and ex vivo data (6,7). However, despite the clear potential in using skin as a target for gene therapy, the major technical problem of an in vivo method of gene delivery remains mostly unresolved. Since the stratum corneum (SC) acts as a significant physical barrier against molecular transfer into the skin, the technical problem of how to deliver molecules as large as genes through this layer still persists. This chapter describes an in vivo method using pulsed electric fields to deliver naked reporter genes into the skin as "proof of principle." [ABSTRACT FROM AUTHOR]

Drug delivery across skin offers advantages over conventional modes of administration. It avoids gastrointestinal degradation and the hepatic first-pass effect, has potential for controlled and sustained delivery, is user-friendly and therefore improves patient compliance (1-2). However, because the skin's outer layer, the stratum corneum, is an extremely effective barrier, transdermal transport of most drugs is very slow, exhibits lag times of hours and steadystate rates that are often subtherapeutic. Chemical and physical approaches to increasing transdermal transport have been explored. Recently, the intermittent application of short (e.g., milliseconds), high-voltage (e.g., 100 V across skin) pulses has been shown to increase transport across skin by several orders of magnitude on a time scale of minutes, probably by a mechanism involving electroporation (3-6). [ABSTRACT FROM AUTHOR]

The main barrier to cutaneous or transcutaneous drug and gene delivery is the impermeability of the stratum corneum (SC), the outermost layer of the skin (1). If the integrity of the SC is disrupted, the barrier to molecular transit may be greatly reduced. Cutaneous absorption can be increased by removal of the SC by tape-stripping or dermabrasion, by vehicle (solvent-carrier) optimization, or by the use of penetration enhancers like DMSO (dimethylsulfoxide), oleic acid, and alcohols (2,3). An electric field can also be used to enhance delivery. Disruption of the SC can be achieved by electroporation, which is the creation of penetration sites by an electric pulse. Ions and molecules move through induced gaps of the SC by diffusion and electromotive or electroosmotic transport (4-6). Electroporation differs from iontophoresis, in which there is an increased migration of ions or charged molecules through the skin when an electrical potential gradient is applied. The primary transdermal route for iontophoresis seems to be appendageal or intercellular through preexisting pathways (5,7), or as a result of low-voltage (<5 V) induced permeabilization of appendageal bilayers (8). A third form of electroenhanced drug delivery, electrochemotherapy (9), refers to localized delivery of electric pulses across a tumor following systemic or intratumor drug administration, and usually does not involve cutaneous or transcutaneous delivery. [ABSTRACT FROM AUTHOR]

The stratum corneum, the outermost layer of the skin, acts as a barrier between the skin and the outside world, preventing evaporation of water from underlying tissues while impeding the diffusion of foreign molecules into the body (1,2). Densely packed layers of flattened, dead, keratinized cells (2,3) are incorporated into a lipid lamellae matrix consisting primarily of ceramides, cholesterol, and fatty acids (2,4), forming an impermeable, hydrophobic partition. The stratum corneum represents the main obstacle to efficient transdermal drug delivery (1,2). If the stratum corneum is disrupted, the barrier to molecular transport is greatly reduced. [ABSTRACT FROM AUTHOR]

In many in vitro transdermal drug delivery experiments, the skin is placed within a permeation chamber, and measurements are taken every hour or so. However, during skin electroporation, significant molecular transport can occur within the first few minutes (1). [ABSTRACT FROM AUTHOR]

Transient disruption of skin's barrier properties using high-voltage pulses involves complex changes in skin microstructure believed to be due to electroporation. Electroporation of cell membranes is a well known phenomenon which has found extensive use as a method of DNA transfection in biological laboratories (1-3). More recently, it has been shown that the multilamellar lipid bilayer membranes found in skin can also be electroporated (4-17). The dramatic and reversible increases in skin permeability caused by electroporation indicate that drugs might be delivered transdermally at significantly enhanced rates. Especially for macromolecules, such as protein- and gene-based drugs, electroporation-mediated transdermal drug delivery could be an important pharmaceutical approach. [ABSTRACT FROM AUTHOR]

In chicken embryos, viral vectors have been successfully used to transfer foreign genes in somatic cells. By using retroviral vectors, for example, genes involved in myocyte growth and differentiation in chicken embryos have been characterized (1-3). The reason for the use of viral vectors is its high efficiency of gene transfection, particularly when stable gene expression is desired. However, if only transient gene expression is considered, several nonviral methods may be useful at present. In ovo lipofection gave spatial expression of a reporter gene in embryonic tissues of chickens (4-6). In addition, two other nonviral methods may be applicable to chicken embryos in ovo. One is microparticle bombardment which has been widely used to transfect genes to tissues of a variety of animal species in vivo (7,9), and the other is electroporation (EP) by which foreign genes are transferred into cells through nanometer pores made on the cell membrane by applying electric pulses (10). The latter method is found to be more efficient than other nonviral methods (11), and has been tested in various animal tissues such as the rat brain, the mouse testis, and the chicken embryo (12,14). [ABSTRACT FROM AUTHOR]

Hemophilia B is an X-linked genetic disorder that typically results from chronic circulating deficiency of blood coagulation factor IX (FIX) (1). While the occurrence of hemophilia B is significantly less frequent than hemophilia A (factor VIII, deficiency) it has received special attention as a model for gene therapy. This is because hemophilia B is one of the least complicated genetic diseases from the point of view of demonstrating the proof of principle of a gene therapy protocol. Specifically, hemophilia B is a single gene recessive disorder and a wide range of tissues can be targeted for FIX gene delivery and strict regulation of FIX expression is not required. In addition, the 2.8 kb FIX cDNA is much smaller than the 9 kb FVIII cDNA, and FIX expression in transfected mammalian cells has been less problematic than FVIII expression (2). Since clinical severity of bleeding episodes closely corresponds to a patient's FIX activity, achieving even partial restoration of normal FIX levels in the bloodstream can alleviate internal bleeding. Individuals with FIX levels less than 1% of normal experience severe symptomatic episodes but providing roughly 5% of normal levels (i.e., 250 ng/mL plasma) can significantly reduce the frequency and severity of bleeding episodes and reduce long term complications (3). Treatment of hemophilia B primarily relies on intravenous injections of FIX protein purified from pooled human plasma, or very recently, on newly developed recombinant FIX. Treatment is applied typically only when bleeding episodes have occurred or are expected, for example, in case of a trauma or surgery. Although the risk of viral transmission of HIV and hepatitis viruses has been largely eliminated the absolute safety of any product derived from blood cannot be guaranteed. Furthermore, supplies of factor concentrates are limited and costs (especially if prophylactic treatment is being considered) are high. Thus, the application of gene therapy to hemophilia, whereby long-term correction of factor IX deficiency might be achieved, would be extremely useful. [ABSTRACT FROM AUTHOR]

Until today, gene transfer to germ cells has been attempted by a variety of methods including microinjection, embryonic stem cell-mediated transfection, virus mediated transfection, lipofection (1), microparticle bombardment (2), and sperm mediated transformation (3). In vivo gene electroporation (EP) now is a viable option for gene transfer purposes as demonstrated by strong shortterm gene expression and long-term expression after gene transfer (4,5 and unpublished). In vivo gene EP is simple and convenient. Adequate development and differentiation of transfected cells can be maintained in the in vivo environment. Furthermore, it can be applied, in principle, to any types of cells and tissues so long as the target is accessible. The advantages of in vivo EP over other nonviral methods such as lipofection and microparticle bombardment are: possible tissue damage is less; there is no limitation of DNA to be transfected at a time; and DNA can be transferable to cells deep inside the target tissue. [ABSTRACT FROM AUTHOR]

Electrochemotherapy has been proven to be efficient for the treatment of subcutaneous tumors of different histological types in mice, rats and cats (1-3). Electrochemotherapy is essentially a local treatment. Indeed, it is based on the potentiation of the cytotoxicity of a low-permeant drug, typically bleomycin, by tumor cell permeabilization using brief and intense electric pulses. In the tissues exposed to such electric pulses, the so-called cell electropermeabilization is obtained only in the volume crossed by an electric field of intensity higher than a threshold value (4). The existence of this threshold for tissue permeabilization implies that the potentiation of the cytotoxic drug by the applied electric pulses is limited to the space roughly comprised between the electrodes. In the case of rather small and prominent cutaneous or subcutaneous tumors, it is easy to place two external electrodes on each side of the tumor nodule to be treated and to transcutaneously deliver the permeabilizing electric pulses. For thick and for deep subcutaneous tumors as well as for tumors located in internal organs, this electrode configuration is not appropriate because the electric pulses have to be delivered directly to the tumor tissues. Externally placed electrodes simply do not supply electric fields that extend deep enough for these situations. Intratumoral electric pulse delivery can, however, be achieved using needle-electrodes that are inserted into the tumor volume. We have designed an applicator constituted by multiple parallel and equidistant needles in order to avoid the delivery of very high-voltage electric pulses. A specifically manufactured generator ensures the multiplexed supplying of the electric current to each pair of closest needle electrodes. Thus, the entire tumor volume is divided in small units which are separately permeabilized by the different pairs of closest electrodes. [ABSTRACT FROM AUTHOR]

Gene therapy is a relatively new type of treatment compared to other modalities such as surgical intervention and drug therapy. Unfortunately, gene therapy is not yet a reality. However, this type of treatment continues to show promise due to the wealth of molecular information about human disease that has been accumulated in the past two decades. This information has a high potential for therapeutic benefit because the molecular basis for many diseases has been identified (1-3). It is clear that the introduction of DNA that codes for therapeutic translation products is a rational strategy for correcting diseased or dysfunctional cells. This type of therapy, gene therapy, is particularly promising for the treatment of cancer and metabolic diseases. It also has a high potential for vaccination against disease. [ABSTRACT FROM AUTHOR]

Electrochemotherapy (ECT) is a combination treatment which involves administering a chemotherapeutic agent followed by the delivery of electric pulses to cells or tissue. Electrical treatment results in increased drug uptake by the cells which provides an improved therapeutic benefit relative to using the drug alone. Increased drug uptake is due to a process that has been termed electropermeabilization, or electroporation. [ABSTRACT FROM AUTHOR]

The first attempt to apply electrochemotherapy (ECT) to the brain was reported in 1993 by Salford et al. 1993 (1). They managed to significantly prolong the survival of RG2 glioma bearing Fischer-344 rats by 200% by iv administration of bleomycin followed by intracranial electrochemotherapy with exponential decaying pulses. In collaboration with the department of tumor immunology, Lund University, an ethyl-nitroso-urea induced rat glioma cell line (N32) is developed that produces glioma of malignant astrocytoma type with only half the growth rate of the RG2 cells (2). The N32 tumor implanted in rats was treated with intracranial electrochemotherapy and enhanced uptake of [111In]bleomycin from intracranial ECT was also demonstrated with a scintillation camera (3). 111In-labeled bleomycin has been used to investigate the uptake and retention after ECT treatment of subcutaneous N32 tumors (4). [ABSTRACT FROM AUTHOR]

Preclinical experiments performed on mice clearly showed that electrochemotherapy can efficiently treat subcutaneous tumors of different histological types (1-4). However, the possibility of relevant clinical applications for electrochemotherapy requires the demonstration of its efficacy as a treatment of tumors larger than those encountered in mice. This necessitates the use of tumors growing in animals that are larger than mice. Since models for such tumors are rare and expensive, a convenient possibility is to test electrochemotherapy on spontaneous tumors that veterinarians have to treat in clinical presentations. Among them, cat soft-tissue sarcomas constitute a set of closely related tumors (fibrosarcoma of grade I or of grade II, and malignant fibrohistiocytoma) which are well suited for electrochemotherapy trials. Indeed, they are subcutaneous tumors, which always escape the conventional surgical treatment after a more or less long time, but which have only a local development for a long period of the disease evolution. Thus this carcinologic situation provides the possibility of testing the local efficiency of electrochemotherapy on animals having a good health status and bearing tumors for which no further conventional therapy can be proposed (5). [ABSTRACT FROM AUTHOR]

It has been reported that the application of strong electric fields across a cell results in the formation and expansion of temporary membrane pores. Electrochemotherapy is a method which enhances the effectiveness of chemotherapeutic agents by administrating the drugs in combination with short intense electric pulses (1). Cell electropermeability allows nonpermeant or weakly permeant drugs to enter the cells. Electrochemotherapy is effective because electric pulses permeate any type of tumor cell membrane in vitro and in vivo. We have shown that electropermeabilization induces a twofold increase in the concentration of Bleomycin, in bladder cancer cells in vitro and in normal bladder tissue of rats in vivo (2). Here we introduce our method to assess the effectiveness of this therapy for rat's bladder cancer. [ABSTRACT FROM AUTHOR]

Each year approximately 6000 new cases of soft tissue sarcoma are diagnosed in the United States (1). The disease affects the extremities in 60% of the reported cases with the lower extremity the most likely tumor site (2,3). Management of soft tissue sarcomas is challenging but over the last 20 yr treatment has evolved from radical procedures such as amputation or compartmental resection to limb-sparing approaches (4,5). However, current limb sparing procedures are not applicable to all adult soft tissue sarcomas of the extremity. Limb sparing techniques are not employed when tumors are located close to joints, bone, or neurovascular bundles (6). [ABSTRACT FROM AUTHOR]

Bleomycin has, in the years of developing electrochemotherapy (ECT), proven to be an extremely potent drug for this cancer treatment modality and is also the most frequently applied chemical agent. It is of importance to investigate the pharmacokinetics of bleomycin under normal conditions and particularly in combination with ECT. [ABSTRACT FROM AUTHOR]

Electroporation (also termed electropermeabilization) of muscle tissue has been studied in several contexts. It has been shown that electroporation plays an important role in muscle damage as a result of electrical injury (1,2) and that electroporation of cardiac muscle occurs during defibrillation or cardioversion (3,4). As electroporation has been shown to greatly enhance the cytotoxic effect of certain chemotherapeutic agents, and as clinical Phase I-II studies (5-8) have shown that the combination of electroporation and chemotherapy (electrochemotherapy) is highly efficient against various localized cancers, the question of normal tissue sensitivity to electroporation needs to be investigated. Finally, efficient in vivo gene transfection to muscle tissue by electroporation has recently been reported (9,10), warranting increased knowledge on in vivo electroporation of muscle tissue. [ABSTRACT FROM AUTHOR]

Cancer of the pancreas is currently the fifth leading cause of cancer related deaths with a five year survival of less than 1% In the United States (1). It is one of the most difficult cancers to treat, since it is hard to detect in the early stages. The patients remain asymptomatic until late in the course of the disease. An excellent review of pancreatic carcinoma has appeared (2). Despite the progress made in our understanding of the biology of this cancer (3), the final outcome for this disease has remained extremely poor. Conventional chemotherapeutic agents have not been very effective for human pancreatic adenocarcinoma (4). Use of intratumoral chemotherapy in combination with monoclonal antibodies have been reported to produce better response rate and also reduced toxicity (5,6). Smith and colleagues (7) have recently shown that an injectable gel with a sustained release profile can inhibit tumor growth in vivo in human pancreatic cancer xenografts. This was demonstrated in nude mice with BxPC-3 xenografts using fluorouracil, cisplatin, and doxorubicin with a consequent size reduction of the tumors between 72% and 79%, compared to the controls at day 28 after the first treatment. Although these figures are impressive, by any standard, no cure was reported. [ABSTRACT FROM AUTHOR]

Electrochemotherapy has been developed on the basis of in vitro data showing the huge increase of bleomycin cytotoxicity observed after cell electropermeabilization. Electrochemotherapy has been proven to be highly efficient as a local antitumor treatment on transplanted tumors (1). Indeed, electrochemotherapy resulted in high rates of tumor responses and even cures in preclinical trials on different experimental murine tumors (2). Treatment efficacy results from the local application of adequate electric pulses able to permeabilize the tumor cells located in the tissue volume crossed by the electric field, which allows the bleomycin present in tumor interstitial fluids to enter these cells and to kill them (3). Since the electric pulse delivery is designed to only reversibly permeabilize the tumor cells, electrochemotherapy is almost devoid of any side effects, and it can be safely proposed as a new antitumor treatment to be used in human clinics. Actually, a phase I-II clinical trial of electrochemotherapy has already given very satisfactory results on cutaneous tumors (4). [ABSTRACT FROM AUTHOR]

In order to be effective, electrochemotherapy must meet the following two requirements. First, the chemotherapeutic drug must be present around tumor cells, and second, each cell in the tumor must be exposed to an electric field that is above the threshold value for this particular tumor type. [ABSTRACT FROM AUTHOR]

In vitro data have shown an increased cytotoxic drug uptake into electropermeabilized cells in suspension, leading to a marked cytotoxicity increase (1). Preclinical experiments were required to demonstrate the in vivo applicability of these observations. Obviously, the most convenient laboratory animal model to test new antitumor treatments is the mouse. Indeed, there exist many tumors of different histological types which can be transplanted in mice, either in immunocompetent mice in the case of syngeneic tumors or in immunodepressed mice in the case of allogeneic or xenogeneic tumors. From a practical point of view, mice have the advantage to be rather cheap and to allow a large number of experiments. Moreover, murine tumors are generally easy to transplant, grow rapidly, and can be conveniently followed for their evolution, at least in the case of subcutaneous tumors. Finally, murine subcutaneous tumors are well adapted to test the antitumor effects of electrochemotherapy since they allow the use of a rather simple material to conveniently apply transcutaneous permeabilizing electric pulses. [ABSTRACT FROM AUTHOR]

Human skin is a complex system, providing a formidable obstacle to drug delivery Fig. 1 (1-3). In particular, the stratum corneum (SC) is the primary barrier to transdermal drug delivery. The stratum corneum is made up of corneocytes, which are flattened remnants of cells, surrounded by lipid bilayer membranes (2,3). Because lipid-based structures tend to exclude charged species, the multilamellar arrangement acts as a "brick wall" (4) to prevent ionic and molecular transport. [ABSTRACT FROM AUTHOR]

The mechanism by which high-voltage pulses transiently disrupt lipid bilayers in cell membranes has been the subject of controversy since electroporation was first observed almost three decades ago. Determining the mechanism by which such pulses permeabilize the complex, multilamellar bilayer structures in skin poses an even greater challenge. To address this issue, a range of methods have been employed to perform biophysical characterization for skin electroporation studies. In this chapter, we provide an overview of these methods and highlight representative findings which biophysical characterization has yielded. [ABSTRACT FROM AUTHOR]

The first research that focused on the effects of pulsed electric fields on living cells described the phenomena of reversible and irreversible membrane breakdown in an in vitro environment in the 1960s and 1970s (1-6). This early research led to the current understanding that exposing cells to intense electric fields induces a transmembrane potential that is superposed on the resting potential. Induced potentials of sufficient magnitude cause a dielectric breakdown of the membrane. This physical phenomenon was termed electroporation, or electropermeabilization, because it was observed that molecules that do not normally pass through the membrane gain intracellular access after the cells were treated with electric fields. [ABSTRACT FROM AUTHOR]

Electroporation generally refers to the technique of permeabilizing cell membranes by applying a short and intense electric pulse across a cell, such that the barrier function of the membrane is instantaneously compromised. During such time, genetic materials may travel across the membrane. For a successful gene transfer process, the barrier function of the cell membrane is rapidly restored, and the cell survives. The electrotransfection process thus comprises two steps. The first step is electroporation, which is governed by the electrical properties of the cell and the suspension medium. The controlling parameters are mainly electrical. The second step is recovery, which must take into account the biological characteristics of the cells. We consider these two steps in this chapter. [ABSTRACT FROM AUTHOR]

Chemotherapy is a standard treatment for a wide variety of cancers. However, response rates are usually low. In melanoma, for example, partial response rates range from 20-45 % with complete responses of less than 5% (1-4). The cell membrane can be a significant barrier for agents with an intracellular site of action. The inability to cross the cell membrane and enter the cell could lead to a low response rate. The effectiveness of these agents could be enhanced if combined with a procedure that increases the permeability of the cell membrane. [ABSTRACT FROM AUTHOR]

The major disadvantage of clinically established chemotherapeutic agents is their lack of selectivity for tumor cells. Therefore, for a pronounced antitumor effect, high doses of the chemotherapeutic drugs are needed, which often cause systemic toxicity and severe side effects. Some chemotherapeutic drugs do not exert their antitumor effects because they have hampered transport through the plasma membrane, but once inside the cell, they can be very potent. To overcome membrane restriction, much effort has been put into the development of drug delivery systems. These systems are aimed at facilitating the delivery of a chemotherapeutic drug into tumor cells at concentrations that are sufficient for effective cell killing and, at the same time, to minimize the drug concentration in normal tissue. [ABSTRACT FROM AUTHOR]

Antitumor electrochemotherapy is a treatment of solid tumors which combines a cytotoxic nonpermeant drug, like bleomycin, with locally delivered permeabilizing electric pulses (1-3). More generally, a new form of vectorization is achieved by the combination of nonpermeant molecules with intracellular targets and of a physical perturbation that locally permeabilizes the cells. This vectorization does not require chemical, biochemical or biological modifications of the targeted compound, since the modification is performed on the target cells. A very convenient way to transiently permeabilize the cells is the use of appropriate electric pulses (short and intense squarewave electric pulses) that are not cytotoxic by themselves (1). These electric pulses reversibly permeabilize the electropulsed cells. Consequently, they allow increased drug delivery inside cells, particularly in the case of drugs for which the plasma membrane is a barrier that limits their access inside the cell [termed nonpermeant drugs] (4). As illustrated in the various protocols reported in this volume, electrochemotherapy using bleomycin is efficient to eradicate subcutaneously transplanted and spontaneous small tumors in mice and rats as well as experimental internal tumors transplanted in rat brain or in rabbit or rat liver. All the clinical trials (3,5-10) confirm the efficacy of this new therapeutical approach based on an original way to deliver nonpermeant cytotoxic drugs [ABSTRACT FROM AUTHOR]

The permeability of a cell membrane can be transiently increased locally when an external electric field pulse with an overcritical intensity is applied. A position dependent modulation of the membrane potential difference is induced during the pulse. A local membrane alteration is created, which may reseal. Its molecular definition remains unknown. This phenomenon is now commonly known as electroporation or electropermeabilization. The former term implies that physical pores are created in the lipid matrix. However their existence has never been clearly demonstrated. The term electroporation is therefore rather misleading. [ABSTRACT FROM AUTHOR]

Electropermeabilization of cell plasma membrane is a threshold phenomenon. When a cell is exposed to electric field a spatially dependent transmembrane potential is induced (1). Above a certain threshold value of transmembrane potential permeability of plasma membrane drastically increases. Thus, in order to obtain plasma membrane permeabilization an above threshold transmembrane potential needs to be obtained. This is achieved by an above threshold electric field intensity. Electropermeabilization is therefore characterized by electric field intensity, but also by the duration and number of applied pulses, as well as their shape (2). Electric field intensity of the pulses of selected duration must reach a threshold, typical for a particular type of cell (3). This threshold is also different for the cells in tissue compared to the threshold for electropermeabilization of the membrane of isolated cells (4). Selected electric field intensity, appropriate for electroporation, should at the same time not exceed the value which will cause irreversible permeabilization or even death of the cell (5). This is particularly important for electro-gene transfection. [ABSTRACT FROM AUTHOR]

Electroporation (EP) of drugs and genes into cells in vitro became a standard procedure in molecular biology laboratories in the last decade. Numerous protocols aid the researcher in selecting appropriate procedures; commercial instrumentation is readily available and discussed (1). The more recent transition to applying EP to living tissue poses a new set of requirements and few practical guidelines are available. [ABSTRACT FROM AUTHOR]

The phenomenon of membrane electroporation (ME) methodologically comprises an electric technique to render lipid and lipid-protein membranes porous and permeable, transiently and reversibly, by electric voltage pulses. It is of great practical importance that the primary structural changes induced by ME, condition the electroporated membrane for a variety of secondary processes, such as, for instance, the permeation of otherwise impermeable substances. [ABSTRACT FROM AUTHOR]

Cell-cell electrofusion (CCE) is a process that involves forcing cells into close juxtaposition and then inducing fusion by delivering electric pulses to the cells. CCE has proven to have many practical applications. It has been used for monoclonal antibody (MAb) production (1,2), hybridoma production (3-5), and to transfer membrane-surface markers (6). Many other applications are described in this volume. In addition, the study of membrane fusion mechanisms has been the focus of some researchers (7-12). Electrofusion techniques seldom result in 100% yield between fusion partners. Therefore, a major aspect of CCE applications is the ability to detect and quantitate fusion products. [ABSTRACT FROM AUTHOR]

Cell-cell electrofusion (CCE) is a process that involves forcing cells into close juxtaposition and then inducing fusion by delivering electric pulses to the cells. CCE has proven to have many practical applications. It has been used for monoclonal antibody (Mab) production (4,5), hybridoma production (1-3), and membrane surface marker transfer (6). Many other applications are described in this volume. In addition, the study of membrane fusion mechanisms has been the focus of some researchers (7-12). Electrofusion techniques seldom result in 100% yields between fusion partners. Therefore, a major aspect of all CCE applications is the ability to detect and quantitate fusion products. [ABSTRACT FROM AUTHOR]