At the Boechler Research Group, we study self-assembled surface acoustic wave metamaterials. In particular, we are conducting experiment-driven studies on the convective self-assembly process of silica microspheres. It is expected that by focusing on key parameters, the self-assembly process can be better understood, monitored, and adjusted. Understanding such processes can lead to better metamaterial assembly techniques. Our materials are produced utilizing a wedge-cell self-assembly process. Water containing microspheres is left to dry between two angled glass slides. When the liquid solution between the slides evaporates, capillary forces pull the microspheres toward the water line where they will closely pack together. Depending on the conditions of the surrounding environment, tilt of the wedge-cell, and the surface of the substrate, different formations are observed. Results vary for formation. In general, higher levels of humidity create monolayers of microspheres, with the level being increased the smaller the particle and decreased the larger the particle. Patterns such as ripples occur depending on several variables, including temperature, humidity, and microsphere concentration, usually forming on the edges of the wedge cell. Free-standing membranes can be observed when a TEM grid is placed on the substrate of a wedge-cell that would otherwise generate a microsphere monolayer. These results provide insight into the physics of the self-assembly process and the interactions between microspheres. Materials such as these have the potential to be used in future signal processing devices, protective coatings and armors, and biosensors.

Protonic activity is an essential driving force for processes in cellular biology, including the production of ATP. Palladium (Pd) can uniquely interact with protons (H+) in solution due to its ability to selectively react with H+ to form palladium hydride (PdHx) according to Pd + xH+ + xe- <--> PdHx. As such, PdHx is a versatile bioprotonic transducer for bioelectronics applications. Here, we enhance the rate of the electrochemical reaction of Pd with H+ by adding a Nafion film. The Nafion film acts to increase the local concentration of H+ at the Pd surface, reducing the required potential to produce PdHx. In addition, we demonstrate the exchange of cations, such as H+ and Na+, between Nafion and solution to change the concentration of H+, or pH of solution. This cationic exchange with solution, coupled with the selective injection or removal of H+ using PdHx electrode, could be used to modulate the pH of solution using only the applied potential.

Carboxylic acids are ubiquitous in chemistry and find use in a variety of applications in both industry and in academic research, including as polymer precursors, synthetic building blocks, and food preservatives. Modern routes to synthesize these compounds often involve harsh conditions or reagents harmful to both the environment and human health. An alternative synthetic route is the aldehyde-water shift reaction; in this relatively unknown reaction, an aldehyde is oxidized by water to a carboxylic acid with release of hydrogen gas. The use of water as both solvent and reagent and the mild reaction conditions could potentially reduce the impact of aldehyde oxidation on the environment. Two major classes of half-sandwich catalysts for this reaction have been investigated for activity in catalyzing this reaction with a variety of aldehyde substrates: one series of catalysts features iridum, rhodium, and ruthenium metal centers with bipyridine ligands, while the other series features diamine ligands on ruthenium. Using ¹H NMR and GC-FID to analyze reaction products, many of the catalysts were observed to disproportionate aldehydes to alcohols and carboxylic acids in competition with the desired oxidation to carboxylic acids. Mechanistic studies and catalyst optimization for selective dehydrogenative oxidation are presented.

Gene therapy is one of the most promising methods of cancer treatment being developed. The construction of a reliable and efficient vector to deliver therapeutic genes is a critical aspect to the success of this method. Viral vectors have met some success in clinical trials, but there remain many drawbacks, including inaccurate delivery of DNA, potential for immune response, overexpression of genes, and concerns about their overall safety. These limitations have led researchers to develop non-viral gene delivery vectors as an alternative. Here we report the co-precipitation synthesis of iron oxide nanoparticles (NP) functionalized with a biodegradable copolymer coating containing a cationic polymer block capable of condensing DNA for gene therapy applications. The modification of the copolymer with high affinity iron ligands promoted rapid, reproducible production of NPs without the need for lengthy post synthesis modification. We evaluated a range of polymer to iron ratios to fine-tune both size and zeta potential of the NP to yield the most effective particles for DNA binding and in vivo delivery. NPs produced at the most promising polymer ratios were complexed with DNA at ratios of 2, 5, 10 and 20 to 1 NP:DNA and additional size and zeta potential measurements were carried out to determine stability of NP:DNA complexes over the range of binding ratios. Size and zeta potential optimized NP:DNA complexes were further tested in vitro using a red fluorescent protein encoded DNA plasmid to determine transfection efficiency. After many rounds of optimization, this synthesis approach proved capable of providing great control over surface properties and produced an efficient transfection agent. This approach contains a plethora of possible clinical applications, and holds potential to make gene therapy a more plausible treatment option.

Evolution has selected for an array of structurally similar sterols in the cell membranes of various life forms. While mammalian cells rely on cholesterol, fungi utilize ergosterol, and plants incorporate a variety of different phytosterols. Minor changes in sterol structure are known to have a large impact on their solubility in a membrane. In my research, I use fluorescence microscopy to correlate the structural features of ergosterol, stigmasterol, ß-sitosterol and cholesteryl hemisuccinate with the miscibility temperature of model cell membranes containing two phospholipids (DOPC and DPPC) and one of the aforementioned sterols. I map the full ternary phase diagram of each system and compare it with that of the well-characterized DOPC/DPPC/cholesterol system. Our data reveal that minor changes in sterol structure dramatically impact membrane miscibility temperatures. Comparing miscibility temperature differences could provide insight into the intermolecular interactions between sterols and phospholipids.