This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.Cationic liposomes had been reported to facilitate DNA transfer across cell membranes and are considered to be potential non-viral DNA carriers for gene therapy. High-resolution synchrotron x-ray diffraction (XRD) studies show that the efficiency of the liposome gene transfection is associated with the interaction mechanism between DNA and the cationic vesicles. In an effort to rationally design a cationic liposome that could interact with DNA not only by electrostatic forces but by hydrogen bonding, we synthesized novel amphiphilic metal complexes which were able to form vesicles in aqueous media with high cationic charge densities and well-defined hydrogen bonding motifs suitable for binding to the phosphate backbone groups of DNA. The newly formed vesicles have been proved effective for the transfection of the Green Fluorescent Protein (GFP) pEGFP-N1 (4.9 kb) into mammalian HEK 293-T cell lines. Dynamic light scattering (DLS) studies show a liposome diameter increase from 400 nm to 800 nm when they are complexed with linear DNA. Studies done by transmission electron microscopy (TEM) suggest that the cationic liposome interacts with DNA forming an onion-like structure where DNA monolayers are sandwiched between cationic lipid bilayers. In order to confirm this observation we propose to use small angle x-ray scattering (SAXS) where we expect to see the Bragg reflections result from the intercalated DNA layer. The study of the interactions between DNA and the synthetic cationic liposome could help to develop a new theory on the mechanism of liposome assisted cell transfection.
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