Study Of Cationic Lipid Vesicles And Glycosylated Liposomes

Vesicles are hollow spherical structures formed by the self-assembly of surfactants, lipids, or block copolymers in aqueous solution. They have long been of interest to the scientific community because of their structural resemblance to biological membrane model: the "bulk" solution outside vesicles, the inner chamber, the outside surfaces or hydrophobic palisade layer of vesicles. As a kind of supramolecular aggregate, vesicles have shown wide potential applications in drug delivery, inorganic nanomaterials synthesis and biomembranes simulation.Vehicles for gene delivery have successfully demonstrated the delivery of exogenous genes in vivo, and they can be divided into two major groups:viral and non-viral vectors. Among the non-viral vectors, cationic lipids have been deeply investigated because of their handy synthesis, low immune response and safety. In order to solve the problem that cationic lipids we synthensized before own unsatisfactory transfection efficiency, we study the stable vesicles spontaneously formed in the mixted surfactant systems. Thus, novel galactose-modified lipids are designed to improve liver targeting and transfection efficiency.Firstly, the catanionic vesicles made of three common anionic surfactants (sodium dodecylbenzene sulfonate, sodium dodecyl sulfonate and sodium dodecyl sulfate) and six double-chained quaternary ammonium compounds with carbamate in aqueous solution are investigated. Here, a systematic investigation with conductivity, dynamic light scattering (DLS) and zeta potential (ζ) was performed. The results indicate the vesicles form spontaneously in the three mixed cationic and anionic surfactants systems with different molar ratios and could be stable for at least six months at room temperature. Zeta potentials show the vesicles whether formed in anionic-rich solutions or in cationic-rich solutions are stable. The spherical vesicle microstructures are determined using transmission electron microscopy (TEM). Pyrene probe is solubilized in non-polar bilayer membrane of the vesicles and the fluorescence intensity is significantly enhanced. Meanwhile analysis is made from the viewpoint of Israelachvili theory and Masaniko molecular geometry structure for spontaneous formation of vesicles.Secondly, vesicles form spontaneously in the mixtures of2,3-Bis (alkylcarbamoyloxy)-N, N-dimethyl-N-(2-hydroxyalkyl) propanyl ammonium chloride (CnPAC) and nonionic surfactant Triton X-100in cationic-rich solutions, which has been demonstrated by electrical conductivity measurements, DLS and negative-staining TEM. Thirdly, a formulation with cationie lipids/DOPE at a molar ratio of2/1,1/1and2/3, liposomes la-If,2a-2f and3a-3f were respectively prepared by conventional thin film evaporation and ultrasonic method. Size and Zeta potential of all liposomes were measured.Fourthly, four hydroxyl-modified cationic lipids were selected as delivery of pGFP-N2to the cervix cells. Size and Zeta potential of liposome/DNA complexes were measured at different mass ratios which were1/1,2/1,3/1,4/1,6/1and8/1, respectively. Delivery of DNA to Hela cells by the liposomes was evaluated by measuring the transfection efficiency and cytotoxicity of lipoplexes. Gene transfection efficiency of liposomes1,2and3-DNA complexes was approximately equal to that of Lipo2000-DNA complex, and a lower cytotoxicity compared with Lipo2000. The largest particle-size occurred at the break point from negative Zeta potential to positive Zeta potential.Finally, in order to solve the problem that galactose ligand1-hydroxy substituted cationic lipids owning unsatisfactory liver target, galactose ligand2-hydroxy and6-hydroxy substituted cationic lipids were designed, and some intermediates were synthesized in this paper. Some significant results were got, which provides foundations and references to the subsequent research.