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Over the last decades, there has been an explosion of interest in plasmid DNA for gene therapy with reports of their efficacy in the fight against cancer, vascular diseases, and inherited diseases caused by specific gene defects (Srivastava, 2003). DNA plasmids present several advantages over the use of recombinant viruses concerning their production and safety issues. Plasmid DNA vectors can be constructed easily and economically, and they are free of size constraints imposed by viral packaging, obviating the need for an infectious vector and lessening the likelihood of toxicity and immunogenicity (Davis, 1993). Plasmids have a relative low cost, long shelf life and allow repetitive administration of the therapeutic gene without generating an immune response against the delivery vector (Donnelly, 2003). Finally, plasmids can be injected directly into tissues, such as heart (Sarkar, 2002), muscle (Neumeister, 2001, Dan, 2000) and tumors (De Marco, 2003, Sasaki, 2002).