| The properties of cationic lipids and polymers are being investigated for their role in mediating nonviral gene delivery. These gene delivery complexes are formed through an electrostatic interaction between the negatively charged phosphate backbone of DNA and positive charges of the lipids and polymers. In this thesis, studies of the interaction and kinetics of formation of complexes consisting of two cationic lipids, DDAB and DOTAP, or PAMAM dendrimers with DNA were examined. Additionally, the effects of the structure of the complexes and vehicles on various biological barriers to gene delivery were also explored.; The conformation of DNA complexed with cationic lipid is controversial. Circular dichroism and vibrational spectroscopy investigations of complexes suggest the DNA conformation remains in the native B-form. An overall interpretation of the spectroscopy data in conjunction with molecular modeling, however, suggests the DNA helix is at least locally altered by perturbation of the base/base interactions.; Stopped-flow spectroscopy studies of the kinetics of assembly of both cationic lipid and dendrimer complexes resolved two sequential steps, binding/dehydration and condensation events, in the assembly of complexes. The temperature dependence of these kinetic events yields an activation energy related to the formation of complexes consisting of each polycation. A clear trend in these activation energies exists for the higher generation dendrimers. The binding events follow the trend G4 > G7 > G9 while the opposite trend G9 > G7 > G4 is observed for the condensation event. It is postulated that a balance between a more favorable condensation and less favorable binding may prove beneficial in enhancing gene delivery.; Comprehensive characterization of the structure and interaction between the components of DNA/dendrimer complexes suggests select properties may be important in overcoming cellular barriers to gene delivery. Highly transfecting complexes composed of PAMAM dendrimers have size/zeta potential values between 4 and 8. A clear overall correlation between the biophysical properties of nonviral gene delivery systems and their biological activity is, however, not observed. This may be due, at least in part, to the heterogeneity of these electrostatic complexes. |
