Liposomes gene transfer systems

Nonviral gene transfer systems are based on a variety of technologies that employ physical/chemical means to deliver genes [6], These technologies include direct plasmid injection, bombardment with DNA coated microprojectiles, and DNA complexed with liposomes or polymers. Some nonviral transfection techniques are too inefficient (e.g., coprecipitation of DNA with calcium phosphate [7], DNA complexed with diethylaminoethyl (DEAE)-dextran [8], electroporation [9]), or laborious (e.g., microinjection of DNA [ 10 ]) for clinical use. Only those gene delivery systems (viral and nonviral) with potential for clinical application are discussed in this chapter. The main features of these technologies (Table 18.3) are described and specific examples of their applications highlighted. 

The therapeutic efficacy of either systemic or local pulmonary delivery of the IFN-y gene was evaluated in a murine allergen-induced airway hyperresponsiveness (AHR) model (Dow et al. 1999) and it was found that a high efficiency of gene transfer could be achieved. Intratracheal administered cationic liposomes were prepared from a mixture of l,2-diacylglycero-3-ethylphosphocholine (EDMPC) and cholesterol. Intravenous injections were prepared from l,2-dioleyl-3-trimethylammo-ninm propane (DOTAP) and cholesterol and compared with pulmonary administered... 

Sakurai, F., Nishioka, T., Saito, H., Baba, T., Okuda, A., Matsumoto, O., Taga, T., Yamashita, F., Takakura, Y. and Hashida, M. (2001) Interaction between DNA-cationic liposome complexes and erythrocytes in an important factor in systemic gene transfer via the intravenous route in mice the role of the neutral helper lipid. Gene Then, 8, 677-686. 

Direct gene transfer into the respiratory system can be carried out for either therapeutic or immunization purposes. Cells in the lung can take up and express plasmid DNA whether it is administered in naked form or formulated with cationic liposomes. For a given dose of DNA, the results can be improved when the DNA is mixed with the minimum amount of lipid that can complex it completely. Such a complex formation can be considered a formation of microparticles that can enhance cellular uptake and subsequent immune responses. 

Cationic liposomes composed of 3(3- [ N- (N N-dimethylaminoethane (carbamoyl] cholesterol (DC-Chol) and dioleoylphosphatidylethanolamine (DOPE) (DC-Chol/DOPE liposome, molar ratio, 1 1 or 3 2) prepared by the dry-film method have been often used as non-vtral gene delivery vectors. We have shown that a more efficient transfection in medium with serum was achieved using DC-Chol/DOPE liposomes (molar ratio, 1 2) than those (3 2), and preparation method by a modified ethanol injection than the dry-film. The most efficient DC-Chol/DOPE liposome for gene transfer was molar ratio (1 2) and prepared by a modified ethanol injection method. The enhanced transfection is related to an increase in the release of DNA in the cytoplasm by the large lipoplex during incubation in opti-MEM 1 reduced-serum medium (optiMEM), not to an increased cellular association with the lipoplex. Cationic liposomes rich in DOPE prepared by a modified ethanol injection method will help to improve the efficacy of liposome vector systems for gene delivery. 

Although there are ongoing advances in the development of nonviral delivery systems for gene transfer, liposome/DNA complexes are still the most common and best studied. 

Lipid/DNA particles represent a nonliposomal but lipid-based delivery system for gene transfer. Monomeric or micellar lipids are allowed to interact with DNA in the presence of detergent or some other surface-active agent that is then removed by dialysis. As the surface-active agent diffuses out, solid, condensed particles of lipid and DNA form (17). These can be prepared such that they are smaller and more homogeneous than liposome/DNA complexes yet transfect cells equally well (F. Wong, unpublished observations). 

Hangai M, Kaneda Y, Tanihara H, Honda Y. In vivo gene transfer into the retina mediated by a novel liposome system. Invest Ophthalmol Vis Sci 1996 37 2678-2685. 

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