7.2.2 Non-Viral Techniques with Both In Vitro And In Vivo Applications
7.2.2.1 Liposomes

The liposomes are spheres consisting of lipid molecules surrounding an aqueous interior. The liposomes, is a model where cellular membranes entrapping DNA. The most commonly used liposomes are the Cationic liposomes. Cationic liposomes consists of a positively charged lipid and a co-lipid, which interact with the negatively charged DNA molecules to form a stable complex.(Nabel et al 1993). A number of positively charged lipids are commercially available for example lipofectin. Lipofectin can interact with DNA spontaneously to form complexes that have a 100% loading efficiency. Lipofectin has been used to deliver linear DNA, plasmid DNA, and RNA to a variety of cells in culture.  It was also shown that lipofectin could be used to deliver gene in vivo after injecting the tissues such as lung, and liver. The released DNA can be expressed extrachromosomally within the recipient cell.  (Lasic, 1998) 

The advantages of using this system in gene therapy are numerous such as:

1. The liposomes are stable and available commercially since they offer protection to DNA degradation.

2.  Novel liposomes are easily prepared in bulk.

3. Naked DNA or RNA have high binding efficiency with the no limits to the size, they can carry a large pieces of DNA.

4.  They can transfect most types of cells.

5.  They have no immumogenicity

6.  The recipient cells are not necessary replicating to uptake the DNA.