Synthesis and characterization of star shaped polymers to be used in siRNA delivery

Utilizing the siRNA-based RNA interfering mechanism, suppression of gene expression, in addition to being used to elucidate the basic functioning of specific genes, is a gene therapy application that has an effect on diseases such as viral infections, genetics, cardiovascular diseases and cancer. Cancer is one of the most important and deadly diseases in the world and nowadays threatens thousands of people and these numbers are increasing every year. Although there are many traditional methods for fighting cancer disease, these methods have negative effects on the patients, and researchers who are focused on cancer treatment lead to the development of new treatment strategies. One of the side effects of traditional treatment methods is that destroy cancer cells as well as healthy cells. Recent studies have focused on this problem and developed methods aiming at targeting cancer cells. One of the new generation cancer cell-based methods developed is siRNA therapy. siRNA therapy directly acts as a potential therapeutic agent by acting directly on the problematic gene at mRNA level. However, siRNA has limitations such as it's ability to pass through the cell membrane and not to enter the cell effectively, which makes it difficult to use therapeutically. Moreover, the possibility of siRNA's undergoing enzymatic degradation by nuclease causes the half-life of siRNAs to be quite short. In order to avoid such adverse effects, there is a need to use an appropriate and effective carrier system for siRNA delivery. At this point, the star polymers are effective polymer to remove the need for carrier system and to prevent siRNA degradation. Development of the most efficient system for siRNA delivery with properties such as extraordinary encapsulation capacities for gene load, sphere structure with electrical charge for gene interaction and abundant internal and external active groups for functionalization. Within the scope of the thesis, it is aimed to develop an effective carrier system for siRNAs by synthesizing, functionalizing and characterizing star polymers which will interact with siRNAs. From this point, to reach the determined target, synthesis of star polymers with polyethylene glycol based and nitrogen containing nucleus prepared with ATRP, which is the carrier system, was first carried out. Synthesized star polymers were studied using various characterization techniques and star- shaped polymeric carrier systems were obtained which gave optimum values for siRNA transport. In the second part of the study, the cytotoxic effects of star polymers showing cationic properties on the living cells and gene silencing studies of siRNA loaded cationic particles on the HEp-2 cell line, which is a larynx cancer cell line, were performed in vitro and gene expression on HEp-2 cells was successful.