Studies on Efficiency and Toxicity of in vivo Delivery Systems for siRNA and plasmid DNA

In this dissertation, systemic delivery of NAs, alone and complexed with polycationic delivery systems, was analysed. The analysis was focused on tolerability and efficiency of the treatment. The in vivo administration is so far hampered by the lack of stable delivery systems that are able to protect their NA cargo in the blood stream and savely lead it to the desired target cells. However, two novel polycationic vectors that had been established in our lab, led to promising results for siRNA delivery in vitro. In the current work we have therefore tried to optimize siRNA / polycationic complexes for in vivo administration. Furthermore, we have used the therapeutically relevant RAN siRNA to influence the growth of subcutaneous Neuro2A tumors in an in vivo model. Another aim was to evaluate different biodegradable polymers, that had been established in our lab, for their efficiency and safety in in vivo application. Polymers were compared with L-PEI as a gold standard regarding efficiency. However, L-PEI can not be degraded within the body and can thereby lead to a long-term toxicity. In contrast, we wanted to show that our biodegradable polymers can reach efficiency levels as high as L-PEI, yet compared with a much better tolerability and the possibility of repeated application. Furthermore we were interested in clarifying the impact of the NA on efficiency and toxicity of the treatment. In this case we have compared plasmid DNA containing bacterially derived CpG motifs, with plasmid DNA that was exempt from CpG sequences. But because plasmids are generated in bacteria and the plasmid purification step leaves behind a certain amount of bacterial genomic DNA, we also wanted to clarify the impact of this (CpG containing) impurities. One approach was to compare the effect of the plasmids alone. For this analysis we had chosen the possibility of hydrodynamic tail vein injection of plasmid solutions in mice. Another approach was to compare the plasmids when they were complexed to L-PEI as a gold standard for polyplex deliver