siRNA carriers based on carbosilane dendrimers affect zeta potential and size of phospholipid vesicles

One of the major limitations in gene therapy is an inability of naked siRNA to passively diffuse through negatively charged cell membranes. Therefore, the siRNA transport into a cell requires efficient carriers. In this work we analyzed the charge-dependent interaction of the complexes of cationic carbosilane dendrimers (CBD) and anti-HIV siRNA (dendriplexes) with the model membranes - large unilamellar vesicles (LUV). We used the second generation of branched with CBD carbon-silicon bonds (CBD-CS) which are water-stable and that of oxygen-silicon bonds (CBD-OS) which are slowly hydrolyzed in aqueous solutions. The LUVs were composed of zwitterionic dimyristoylphosphatidylcholine (DMPC), negatively charged dipalmitoylphosphatidylglycerol (DPPG) and their mixture (DMPC/DPPG, molar ratio 7:3). The interaction of dendriplexes with LUVs affected both zeta potential and size of the vesicles. The changes of these values were larger for the negatively charged LUV. CBD-CS resulted in the decrease of zeta potential values to more negative ones, whereas an opposite effect took place for CBD-OS suggesting a different kind of interaction between LUVs and the dendriplexes. The results indicate that both CBD-CS and CBD-OS can be used for transport of siRNA into the cells. However, CBD-CS are preferred due to a better stability in water and improved bioavailability of siRNA on their surface.