Gene delivery systems lipid-based

Outline the various types of lipid-based gene delivery systems. 

Though less studied than synthetic polymer and lipid-based gene delivery systems, there have been significant advances in the field of natural polymers for gene delivery. Biodegradable polymers are less likely to accumulate within tissues than their synthetic counterparts. Synthetic polymers are not easily removed by normal clearance systems and can accumulate in tissues. 

Mahato RI, Rolland A, Tomlinson E (1997) Cationic lipid-based gene delivery systems Pharmaceutical perspectives. Pharm Res 14 853-859. 

To develop an efficient gene delivery system, it seems necessary to understand the extra- and intracellular processes involved in the overall transfection mechanism. This will lead to understanding the mechanism, which is necessary for developing novel lipid-based non-viral vectors. For this purpose, cationic liposomes and pDNA are used widely to understand the cellular mechanism involved in the transfection (Fig. 13.3). 

Pillai R, Petrak K, Blezinger P, Deshpande D, Florack V, Fieimatk B, Padmabandu G, Rolland A. Ultrasonic nebulization of cationic lipid-based gene delivery systems for airway administration. Pharm Res 1998 15(11) 1743-1747. 

Delivery systems for gene-based drugs are needed to fulfill their promise in the medical treatment. Interactions of the potential delivery systems with the lipid bilayers are of crucial importance, since the lipid bilayer barrier must be overcome either at the level of plasma membrane or in the endosomes. 

Lipid bilayers affect drug delivery at several levels of pharmocokinetics, both at macroscopic and microscopic levels. Understanding the structure and function of the bilayers aids in the development of better drug delivery systems. Delivery is particularly important for the success of the gene-based drugs. 

Several enveloped viruses, and some physical gene transfer techniques such as electroporation, deliver the nucleic acid into the cell by direct crossing of the cell membrane. Lipid-based, enveloped systems can do this by a physiological, selfsealing membrane fusion process, avoiding physical damage of the cell membrane. For cationic lipid-mediated delivery of siRNA, most material is taken up by endo-cytotic processes. Recently, direct transfer into the cytosol has been demonstrated to be the bioactive delivery principle for certain siRNA lipid formulations [151]. 

Anwer, K., C. Meaney, G. Kao, N. Hussain, R. Shelvin, R.M. Earls, R Leonard, A. Quezada, A.P. Rolland, and S.M. Sullivan, Cationic lipid-based delivery system for systemic cancer gene therapy. Cancer Gene Ther, 2000. 7(8) 1156-64. 

Polymer. The field of nonviral gene delivery using cationic polymers is at its early stage compared to that of cationic lipid. However, this system is also known to have advantages over lipid-based systems in controlling the size, charge, and other physicochemical properties. Polycation-DNA complexes, also called as polyplexes, are formed by a cooperative... 

---