Thesis(Ph.D.)--Case Western Reserve University, 2009 / Abstract Department of Chemical Engineering Title from OhioLINK (viewed on 20 April 2009) Available online via the OhioLINK ETD Center

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Hong Kong, 2008. / Also available in print.

Thesis (Ph. D.)--University of Oregon, 2007. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 158-174). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (Ph. D.)--State University of New York at Binghamton, Department of Chemistry, 2005. / Includes bibliographical references.

In recent years there has been an increased drive towards point of care testing (POCT), in which assays are performed at the site of the patient. This has many benefits, critically; the time for a result to be obtained will be significantly reduced, allowing for greater and more effective decision making. Many currently used bioassay methods are not affordable in resource poor areas where infectious disease is most prevalent, in order to combat this issue many research groups are attempting to miniaturise equipment for portability and make assays more affordable and therefore more accessible. With the aims of generating a new assay platform which is highly portable and affordable, the work in this thesis presents the development of several generic methods utilising nano- and micro-scale beads coated with aptamer which are then monitored interacting with target proteins with Tunable Resistive Pulse Sensing (TRPS). Aptamers are short oligonucleotide sequences which are capable of binding to a wide range of targets with high selectivity and comparable affinity to antibodies while possessing greater stability and have begun to challenge the role of antibodies. When aptamers bind a target, they often undergo a conformational change. In the assays described herein, this conformational change is key to the observed signal changes. TRPS is a pore-based system in which beads moving through a pore cause a measurable increase in resistance which can be used to derive particle size, concentration, and mobility. During the course of this thesis several template TRPS aptasensors have been developed. TRPS was successfully used to confirm the successful coating of nano- and micro-scale beads with DNA aptamers by monitoring an increase in electrophoretic mobility when the negatively charged DNA is added to the surface. Following on from this, TRPS was used to monitor the interaction of aptamer tagged beads with thrombin protein enabling thrombin detection down to 1.4 nM and the comparison of several thrombin-aptamers with results comparable to previously published SPR data. Thrombin was postulated to shield the negative DNA, resulting in a decrease in mobility, and the magnitude of this charge shielding was found to depend upon the binding mechanism of the aptamer used. This effect is not thought to be specific to our system nor to thrombin, the principles outlined here may be applied to other RPS technologies, or by interchanging of the aptamer, different proteins. In later chapters, this method is expanded to include multiplexed detection of growth factors and a significant improvement in signal. vi Following on from this, the controlled aggregation of avidin coated beads in the presence of biotinylated-BSA was explored. Factors impacting upon this assay were discussed including magnetic separation, particle size and particle concentration, and different methods of data interpretation were presented. This aggregation study identified several key parameters in the use of TRPS in aggregation assays. Using the methods outlined by the study of aggregates, a dispersion assay was then designed in which the interaction of thrombin proteins with clusters of particles brought about the release of many small particles by the disruption of double stranded DNA linkages. This dispersion assay incorporated magnetic separation to simplify the read-out and relied on measuring particle concentration rather than mobility, enabling the use of additional pressure to increase speed and ease of use. Using this method, thrombin was able to be detected down to 100 fM, a significant advancement in TRPS aptasensors.

Nanostructured thin films deposited by magnetron sputtering and gas aggregation sources of nanoparticles are studied especially with regards to their use in biomedical applications. The possibility of using plasma polymers for the preparation of antibacterial coatings is tested first. It is presented that sputtered nylon 6,6 films may be impregnated by antibiotics. The subsequent release of antibiotics from such prepared reservoirs may be tuned by their thickness, chemical composition, or by an additional barrier layer. The second studied type of antibacterial coatings is based on metallic nanoparticles overcoated with sputtered PTFE. It is shown that by a proper choice of the number of nanoparticles and thickness of fluorocarbon overlayer, a significant antibacterial effect can be achieved while maintaining the biocompatibility of produced nanocomposite coatings. The possibility to enhance the antibacterial effect by impregnation of plasma polymer/nanoparticle nanocomposites by antibiotics is also verified. Nanoparticle sources are used to study two-component films with 2D gradient character, too. A simple analytical model is developed allowing description and design of such nanomaterials. Its suitability is experimentally verified on 2D gradients combining Ag and Cu nanoparticles. Finally, an original...

Thesis (M.S.)--Florida State University, 2004. / Advisor: Dr. Yousef S. Haik, Florida State University, College of Engineering, Dept. of Mechanical Engineering. Title and description from dissertation home page (Jan. 13, 2005). Includes bibliographical references.

Thesis (Ph. D.)--State University of New York at Binghamton, Department of Chemistry, 2005. / Includes bibliographical references.

The rise of antimicrobial resistance demands the development of more rapid screening methods for the detection of antimicrobial resistance in clinical samples to both give the patient the proper treatment and expedite the treatment of patients. Cerium oxide nanoparticles may serve a useful role in diagnostics due to their ability to exist in a mixed valence state and act as either oxidizing agents or reducing agents. Considering that cerium oxide nanoparticles have been shown to shift in absorbance upon oxidation, a useful method of antimicrobial resistance detection could be based on the oxidation of cerium oxide nanoparticles. Herein, an assay is described whereby cerium oxide nanoparticle oxidation is a function of glucose metabolism of bacterial samples in the presence of an antimicrobial agent. Cerium oxide nanoparticles were shown to have an absorbance in the range of 395nm upon oxidation by hydrogen peroxide whereas mixed valence cerium oxide nanoparticles lacked an absorbance around 395nm. In the presence the hydrogen peroxide-producing glucose oxidase and either increasing concentrations of glucose or bacterial medium supplemented with increasing concentrations of glucose, cerium oxide nanoparticles were shown to increase in absorbance at 395nm. This oxidation assay was capable of measuring differences in the absorbance of E. coli and S. aureus samples grown in the presence of inhibitory and non-inhibitory concentrations of ampicillin in as little as six hours. Therefore, this cerium oxide nanoparticle oxidation assay may be very useful for use in clinical laboratories for the detection of antimicrobial resistance due to the relatively low cost, no requirement for specialized equipment and, most importantly, the reduced incubation time of the assay to as little as six hours compared to current gold standard antimicrobial resistance detection methods that require 24 hours.; This assay may thus also help partially circumvent the issue of knowledge of antimicrobial resistance in infected patients before prescribing improper regimens.