<p> Glutathione-capped gold nanoparticles of size 1, 3, and 10 nm, CTAB-stabilized gold nanorods, as well as ro-carboxylate-functionalized palladium nanoparticles were synthesized and self-assembled onto graphene oxide to study their coarsening or reshaping behaviors upon heating at different temperatures ranging from 50 &deg;C to 300 &deg;C. These engineered nanoparticle- or nanorod-graphene oxide hybrid materials were studied by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR) spectroscopy, and UV-Vis spectroscopy.</p><p> The spherical nanoparticles would undergo coalescence to become larger particles and the nanorods would undergo reshaping to spherical particles. UV-Vis results show that the plasmonic band of gold nanoparticles at 520 nm would shift to higher wavelength indicating the coarsening into larger particles upon heating. Transmission electron microscopy results were generally in good agreements with the UV-Vis results and would be used as a direct tool to observe the structural changes of gold nanoparticles upon heat treatments.</p><p> Without the presence of graphene oxide, the nanoparticle coalescence began at the temperature between 150 and 200 &deg;C for all three nanoparticles with different core sizes. But with the presence of graphene oxide, nanoparticles start to coalesce at the temperature below 150 &deg;C. The gold nanorods have two plasmonic bands at &sim;780 and &sim;520 nm. The bands at &sim;780 nm for gold nanorods would disappear when the gold nanorods-graphene oxide is heated at 50 &deg;C indicating the complete reshaping of nanorods even at such a low temperature. Gold nanorods themselves are more stable and do not undergo the reshaping completely until the sample is heated above 150 &deg;C. Since graphene oxide is an excellent thermal conductor, we propose that graphene oxide could transfer heat to the nanoparticles and nanorods efficiently, disrupt the interaction of stabilizing ligands, and make them to either coalesce or undergo reshaping at a lower temperature.</p><p> Nanoparticle- and nanorod-graphene oxide hybrid materials were also used to study the effect of covalent and non-covalent interactions between gold nanoparticles or nanorods and graphene oxide during coarsening or reshaping, respectively. Non-covalent interactions were studied by directly adding graphene oxide to aqueous solutions containing water-soluble metal nanoparticles or nanorods, and covalent interactions were achieved by the self-assembly of the same nanoparticles onto thiolated graphene oxide that was prepared by coupling L-cystine using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS). When nanoparticles and nanorods are attached to graphene oxide through additional -covalent bonds, they are more strongly immobilized and therefore would undergo less coalescence and slower reshaping upon heating.</p>

<p> We have developed novel techniques for manufacturing vesicles with predefined attachments to scaffolds of DNA, and have studied the underlying mechanism(s) of this DNA directed vesicle formation by capturing intermediates. These DNA scaffolds are self-assembled by the origami method, which can use DNA as a programmable building block to form diverse structures: two-dimensional crystals, nanotubes, and three-dimensional wireframe nanopolyhedra [1-5]. </p><p> Nano-templated vesicles are prepared using rigid rings of bundled DNA. Single phosphatidyl ethanolamine (PE) lipids are coupled to these rings first by covalent conjugation with an oligonucleotide (oligo) "anti-handle", then by that oligo's sequence-specific hybridization to one of several (0, 1, 2, ..., 16) single-stranded "handles" on the DNA ring, designed to protrude from its interior. Vesicles are then formed in a solution of these ring complexes, excess phospholipid and detergent as the detergent is dialyzed away over several hours. Micelles preferentially nucleate around the alkyl chain of each PE inside the ring, and their growth during dialysis determines the volume of lipid in the final structures formed. Ring-PE lipid-vesicles bear exactly one ring per vesicle in characteristic transmission electron micrographs, with a size close to the inner diameter of its ring template.</p><p> Chapter 1 provides an overview of the significance and roles of engineering membranes in vitro. Biological membranes are incredibly complex, which in turn makes studying structure and function of membrane protein difficult in the absence of an artificial bilayer. Even more so, current limitations of producing high quality liposomes with reproducible techniques are placing more strain on elucidating the mechanisms of reconstitution. However, the emergence of the field of DNA Origami in 2006 truly revolutionized the limitless abilities to create 2D and 3D structures with function. We took advantage of this field by developing geometries to facilitate membrane growth.</p><p> Chapter 2 reports a new method for templating vesicles with a uniform size and shape using DNA origami rings bearing inner handles facing 0&deg; to the center. DNA origami rings of varying diameters can be designed with functional handles for templating the "Saturn" structure. Once the method was established, rings of varying handle angles were synthesized to determine their effects on the final vesicle structures.</p><p> Chapter 3 explores the parameters that affect the quantity of lipids assembling inside the template. These include ultracentrifugation time, detergent to lipid ratio, and dialysis conditions. In order to elucidate the mechanism of formation of our final templated structures, we performed mechanistic studies on 60-nm rings, systematically varying the initial number of lipid molecules anchored inside each ring. The capture of crucial intermediates: circular thin lipidic membrane, lipid bilayer torus, continuous outer bilayer, and seeded small unilamellar vesicles helped us understand how the vesicles are formed.</p><p> Chapter 4 summarizes the main results of the thesis and provides future prospectives on the potential expansion of DNA origami technology. A handful of new opportunities are presented based on control in the organization of DNA materials. Taking advantage of this machinery and applying it to the central problems in engineering, biology, chemistry, physics, and medicine will allow the field to elevate to the next level with promises of becoming a vital area of research.</p>