Electroporation-mediated delivery

Gharty-Tagoi, E.B., et al. 2004. Electroporation-mediated delivery of molecules to model intestinal epithelia. Int J Pharm 270 127. 

Several reports in the literature have indicated that transdermal delivery may be further increased by combining chemical excipients with electroporation. These investigations included macromolecules like dextrans [58], cyclodextrins [59] and even simple salts such as calcium chloride [60]. Other workers have, however, looked at encapsulation of compounds within lipid vesicles (liposomes) as potential candidates for electroporation-mediated delivery [61,62]. A fuller treatment of this combination is described in Chapter 17. 

Chemical Penetration Enhancers of Electroporation-Mediated Delivery.331... 

Several enveloped viruses, and some physical gene transfer techniques such as electroporation, deliver the nucleic acid into the cell by direct crossing of the cell membrane. Lipid-based, enveloped systems can do this by a physiological, selfsealing membrane fusion process, avoiding physical damage of the cell membrane. For cationic lipid-mediated delivery of siRNA, most material is taken up by endo-cytotic processes. Recently, direct transfer into the cytosol has been demonstrated to be the bioactive delivery principle for certain siRNA lipid formulations [151]. 

The two most often used methods for DNA delivery into protoplasts are electroporation and treatment with polyethylene glycol (Paszkowski et al., 1984). The observation that short electric pulses of high field strength transiently permeabilize cell membranes led to the development of electroporation-mediated gene transfer techniques for mammalian cells (Neumann et al., 1982) and plant cell protoplasts (Fromm et al., 1985). Electroporation is now the preferred technique for direct DNA transfer to plant protoplasts. 

Electroporation-Mediated DNA Delivery to Embryos of Leguminous Species... 

Other systems like electroporation have no lipids that might help in membrane sealing or fusion for direct transfer of the nucleic acid across membranes they have to generate transient pores, a process where efficiency is usually directly correlated with membrane destruction and cytotoxicity. Alternatively, like for the majority of polymer-based polyplexes, cellular uptake proceeds by clathrin- or caveolin-dependent and related endocytic pathways [152-156]. The polyplexes end up inside endosomes, and the membrane disruption happens in intracellular vesicles. It is noteworthy that several observed uptake processes may not be functional in delivery of bioactive material. Subsequent intracellular obstacles may render a specific pathway into a dead end [151, 154, 156]. With time, endosomal vesicles become slightly acidic (pH 5-6) and finally fuse with and mature into lysosomes. Therefore, polyplexes have to escape into the cytosol to avoid the nucleic acid-degrading lysosomal environment, and to deliver the therapeutic nucleic acid to the active site. Either the carrier polymer or a conjugated endosomolytic domain has to mediate this process [157], which involves local lipid membrane perturbation. Such a lipid membrane interaction could be a toxic event if occurring at the cell surface or mitochondrial membrane. Thus, polymers that show an endosome-specific membrane activity are favorable. 

To date, a variety of methods have been developed for the efficient delivery of QDs into cells [204, 205]. These include nonspecific endocytosis [206-209] or receptor-mediated endocytosis that involves QDs decorated with transfection reagents (peptides [210-215], proteins [65, 216-219], cationic liposomes [204], dendrimers [204], polymers [220,221] or small molecules [222,223]) that were used for the intracellular delivery of QDs. Physical techniques such as, electroporation [204, 224] or microinjection [204, 225, 226] have also been employed to deliver QDs into cells. 

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