ABSTRACT
Transfection of foreign genes into mammalian cells in vitro and in vivo is the most important technique of gene therapy.1 More than 75% of the clinical protocols involving gene therapy to date employed viral vectors, such as retroviruses (about 50%), adenoviruses (about 20%), adenoassociated viruses, or pox viruses because of their excellent transgene expression. However, despite their high efficiency in vitro, their successful use in vivo is often limited by toxicity, immunogenicity, inflammatory properties, limited DNA size, and reproduction problems of the viruses.1
