Gene Transfer in Mammalian Cells Using Liposomes as Carriers

After understanding the molecular genetic cause(s) for human diseases, gene therapy is a method of treatment under active research. As the name implies, gene therapy involves treatment of diseases by product(s) of foreign gene which return(s) affected cells or tissues to normal status. The successful application of this approach begins with the development of a suitable carrier for the target specific delivery of genetic material followed by expression of DNA at that site. This carrier should also be able to protect the DNA from surrounding environment, e.g., from plasma for in vivo delivery. Under ideal conditions this expression should be controlled by using inducible or tissue specific promoters. Different kinds of systems are being used to effectively transfer and express the foreign DNA in various types of mammalian cells. These are classified below: (i) agents which deliver DNA by physical means: e.g. microinjection (Capecchi, 1980), electroporation (Paquereau and Cam, 1992), biobalistic or particle bombardment (Yang et al., 1990) and jet injection (Furth et al., 1992). (ii) agents which deliver DNA by chemical means: e.g. calcium phosphate (Wigler et al., 1977), DEAE dextran (Ishikawa and Homey, 1992), polylysine conjugates (Wu and Wu, 1987; Wagner et al., 1990), polybrene-dimethyl sulfoxide (Kawai and Nishizawa, 1984) and liposomes (Feigner et al., 1987; Gao and Huang, 1991) (iii) agents which deliver DNA by biological means: e.g. virus derived vectors (Ferry et al., 1991; Culver et al., 1992).