Delivery of pDNA vs siRNA using cationic lipids Sample Clauses

Delivery of pDNA vs siRNA using cationic lipids. Plasmid DNA (pDNa) and siRNA share many similar characteristics; i.e. they are both double stranded nucleic acids, share the negative phosphodiester backbone structure and can both interact electrostatically with cationic lipids. However, there are a few key differences in their physicochemical properties and mode of action that are important when considering how they should be formulated for delivery to cells (Table 1.1). pDNA has a molecular topography which allows it to condense into small particles once the negative charge has been neutralised by the cationic lipid and. On the other hand, siRNA, which is shorter in length and has a more rigid structure, is not likely to condense. Interaction with cationic lipid may result in incomplete condensation and formation of large aggregates (Spagnou, S. et al., 2004). Unlike pDNA, which contains the sugar deoxyribose, siRNA has a hydroxyl group in the second position of the pentose ring instead of hydrogen. The presence of hydroxyl groups makes the siRNA backbone more susceptible to hydrolysis by serum nucleases (Xxxxxxx, X. et al., 2008, Xxxxxx, X., 2005, Xxxxxxxxx, X. et al., 2010). Adequate protection from nucleases is required for both nucleic acids. The difference in site of action gives siRNA an advantage as entry into the nucleus is not required since mRNA molecules are released from the nucleus following transcription (Xxxxxxxx, X.X. et al., 2007, Xxxxxx, X. et al., 2007). Physicochemical Characteristics Cellular stability Site of action Interaction with cationic lipids Gene regulation Large molecular weight (several kilobases) Deoxyribonucleic acid Relatively stable Nucleus Condensation into nanoparticles Upregulation Small molecular weight (21-23 nts) Ribonucleic acid Unstable due to the presence of 2’OH groups Cytoplasm Less condensation Downregulation 1.4.1. Cationic lipid/nucleic acid complex formation