Nonviral transfection vectors

It should be emphasized at this point that the use of physicochemical methods is so far the only way to demonstrate the import of transgene DNA into the mitochondrial matrix in living mammalian cells. The unavailability of a mitochondria-specific reporter plasmid designed for mitochondrial expression severely hampers current efforts toward the development of effective mitochondrial expression vectors. Although any new nonviral transfection system (i.e., cationic lipids, polymers, and others) aimed at the nuclear-cytosolic expression of proteins can be systematically tested and subsequently improved by utilizing anyone of many commercially available reporter gene systems, such a methodical approach to develop mitochondrial transfection systems is currently impossible. 

There is relatively little physical understanding of why certain preparation conditions of nonviral gene vectors generate better gene expression than others [68]. This deficiency has hindered the development of nonviral gene delivery vectors, since relatively few reports quantitatively evaluate DNA complex structure and composition, especially as it relates to gene delivery efficiency. Some structural and physical characteristics, including shape, size, and zeta potential, have been studied for various synthetic DNA delivery systems and have, in some instances, been related to transfection efficiency. 

Transfection of polymer-DNA complexes usually requires actively dividing cells and transfection efficiency is enhanced prior to mitosis, when the nuclear membrane has been broken down. Therefore, gene therapy with nonviral cationic vectors is advantageous in delivery to, for example, brain tumours, where normal cells do not divide and therefore are not transfected, but malignant cells undergo active cell division and are able to be targeted and destroyed. Brunner et al. demonstrated that linear PEI was not dependent on the cell cycle for transfection [63, 64]. 

Nonviral synthetic vectors (cationic liposomes/polymers, dendrimers, cyclodextrin, ceU-penetrating peptides) Vector can cross cell membrane Easy to handle Technically simple Low transfection efficiency and toxicity in certain cases Yes It is possible to perform site directed injections (microinjections)... 

Sequential hydroformylation/reductive amination of dendritic perallylated polyglycerols with various amines in a one-pot procedure to give dendritic polyamines in high yields (73-99%). Furthermore, the use of protected amines provides reactive core-shell-type architectures after deprotection. These soluble but membrane filterable multifunctional dendritic polyamines are of high interest as reagents in synthesis or as supports in homogeneous catalysis as well as nonviral vectors for DNA-transfection (Scheme 18) [65]. 

Genes can be introduced by the application of naked DNA alone however, better efficiency is achieved when the DNA is incorporated into a delivery vector. These delivery vectors consist of viral, those utilizing modified virus particles for DNA delivery, and nonviral, for which various chemicals are used to aid DNA packaging and delivery. Viral vectors confer significantly better transfection efficiency than nonviral vectors however, recently the toxicity and oncogenic side effects of viral vectors have become a major concern (6). Nonviral vectors do not have such serious side effects but lack the efficiency (7). 

Hart SL, Arancibia-Carcamo CV, Wolfert MA, et al. Lipid-mediated enhancement of transfection by a nonviral integrin-targeting vector. Hum Gene Ther... 

The transfection data summarized in Fig. 13 were obtained with primary human umbilical artery endothelial cells (HUAEC). Vascular endothelial cells, acting as an interface between circulating blood and tissues, are known to be involved in inflammatory processes, in atherosclerosis and angiogenesis, and represent a remarkable challenge as a gene therapy target. Their therapy with nonviral vectors... 

Hosseinkhani H, Azzam T, Tabata Y et al (2004) Dextran-spermine polycation an efficient nonviral vector for in vitro and in vivo gene transfection. Gene Ther 11 194-203... 

Stability. Current protocols for nonviral delivery systems call for the preparation of the vector at the bedside, due to their aggregation over time [127-129]. Specifically, aggregation of some lipoplex formulations stored as liquids reduced their transfection efficiency [130,131], Electron microscopy was used to show that PEI/DNA complexes did not aggregate, but vectors made with poly-L-lysine and dendrimers did in one study [103],... 

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