Coupling of experimental and computational approaches for the development of new dendrimeric nanocarriers for gene therapy.

Gene therapy is increasingly critical in the treatment of different types of maladies. The approach of gene therapy can be fundamental in dealing with many kinds of tumors, viral infections (e.g., HIV, HSV), and disturbs linked to genetic anomalies. However, the use of nucleic acids is limited by their ability to reach their action site†"the target cell and, often, the inside of its nucleus. Dendrimers, on the other hand, are an interesting kind of polymers, the general synthetic scheme of which is relatively of recent development (?1980). Among the many possible uses of these polymers, they revealed themselves as great nanocarriers for drugs in general, and particularly for genetic material. Many of the properties of these molecules are directly linked to their structure, and this in turn is critically influenced by their molecular composition. Exploiting in silico techniques, we can reveal many informations about the atomistic structure of dendrimers, some of which are otherwise difficult to gather. The interactions between the carrier and its cargo, and also with all the biological systems that are interposed between the administration and the reaching of the target (e.g., serum proteins, lipid membranes. . . ) are of critical importance in the development of new dendrimers for gene therapy. These interactions can be described and studied at a detail once unthinkable, thanks to the in silico simulation of these systems. In this thesis many different molecular simulation techniques will be employed to give a characterization as precise as possible of the structure and interactions of new families of dendrimers. In particular two new families of dendrimers (viologen and carbosilane) will be structurally characterized, and their interactions with albumin and two oligodeoxynucleotide, respectively, will be described. Then, the point of view of these interactions will be changed: the interactions between a fifth generation triethanolamine-core poly(amidoamine) dendrimer (G5 TEA-core PAMAM) and a sticky siRNA will be studied, varying the length and chemical compositions of the overhangs of the siRNA. Studying dendrimers the use of new molecular simulations techniques were deepened, and such techniques will be employed in other parallel projects. We'll see the steered molecular dynamic method applied in the study of one mutation of the SMO receptor. The development of biological membranes models (that will be used in future to study the interactions of dendrimers with such membranes) was also used to refine and better characterize the ?1 receptor 3D model, previously developed by our research group. A detailed characterization of the putative binding site of this receptor will be given, employing this refined model.