Figure 6.
Common polymer based siRNA delivery systems. (a) Chitosan systems. The RGD modified chitosan nanoparticles (RGD-CH-NP) are reported for targeting siRNA delivery. siRNA/RGD-CH-NPs are prepared based on ionic gelation of anionic tripolyphosphate and siRNA 123, 124. (b) Polycations prepared from polyethylenimine (PEI) or poly-L-lysine (PLL). Their highly cationic nature facilitate strong electrostatic interactions with the negatively of siRNA. PEGylation of polycations with PEG modified with heterobifunctional N-succinimidyl 3-(2-pyridyldithio)propionate allow subsequent coupling of thiolated siRNA via the N-terminal cysteine 136. (c) Micelle-based nanoparticles. Micelles are prepared from the triblock copolymer poly(ethylene glycol)-poly(n-butyl acrylate)-poly(2-(dimethylamino)ethyl methacrylate) (PEGPnBA-PDMAEMA). The presence of amine groups on PDMAEMA allows the electrostatic complexation with siRNA 138. (d) Cyclodextrin containing polymer (CDP). A commonly reported targeted CDP system is prepared through the addition of adamantane-polyethylene glycol-transferrin (AD-PEG-Tf) 153, 155, 157, 158.