Theses and Dissertations

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Open Access
A rapid, point of need open cow test
(Colorado State University. Libraries, 2023) Mendez, Jacy, author; Dandy, David, advisor; Henry, Chuck, committee member; Bailey, Travis, committee member; Hansen, Thomas, committee member
In the dairy industry, maintaining non-pregnant (open) cows is expensive, and may require multiple rounds of artificial insemination (AI) for a cow to become pregnant. There is a need for early pregnancy detection in dairy cows, which allows the use of protocols such as prostaglandin F2-alpha (PGF) and gonadotropin releasing hormone (GnRH) to prepare a cow for another round of breeding via AI, with an emphasis on reduced time between each breeding attempt. The current gold standard method for confirming pregnancy in cows is a rectally-guided ultrasound at day 32 after AI. Interferon-tau (IFNT) is a biomarker that can be detected during days 7-28 of pregnancy in cattle, and is expressed by the cow conceptus. The goal of this work was to develop a cow-side test utilizing IFNT as the biomarker for early cattle pregnancy detection. A lateral flow assay (LFA) was chosen and investigated due to its simplicity and ease of use, but was later adapted to utilize the enzymatic oxidation of 3,3',5,5' – Tetramethylbenzidine to amplify the signal in the test line. C-reactive protein was used to develop protocols for aspects of device development involving nitrocellulose, including antibody striping, blocking, and nitrocellulose selection. These protocols were then utilized as optimization of the lateral flow assay was conducted. The resulting LFA has a limit of detection (LOD) of 10 μg/mL, with an LOD of 100 ng/mL in a half-strip format, with some limitations imposed by false positives. This work provides a novel method of detection for pregnancy in cattle and with further development, has the potential for use by dairy farmers in their respective industry.
Open Access
Brush-like surface using heparin/chitosan based nanoparticles for blood-contacting applications
(Colorado State University. Libraries, 2013) Nijjar, Rajvir Singh, author; Kipper, Matt, advisor; Bailey, Travis, committee member; Reynolds, Melissa, committee member
With increasing applications of biomedical implants, it is crucial to develop surfaces that are blood compatible, meaning they do not induce platelet or protein adhesion. Many implants that are currently used to treat a wide range of problems have one major drawback, they can induce thrombosis. The endothelial glycocalyx plays a crucial role in preventing thrombosis. Based on this idea, we set out to develop a surface that has a brush-like structure similar to that of the endothelial glycocalyx. We developed the surface by adsorbing negatively charged heparin/chitosan polyelectrolyte complex nanoparticles onto a heparin/tri-methylchitosan polyelectrolyte multilayer. The surface was then characterized using surface plasmon resonance (SPR), quartz crystal microbalance (QCM), atomic force microsocopy (AFM), scanning electron microscope (SEM), and polarization modulation-infrared reflection absorption spectroscopy (PM-IRRAS). Using these techniques we confirmed that we had created a surface with brush- like structure. Our hypothesis that the nanoparticles on the surface swell and form a brush-like structure when exposed to physiological conditions seems to be correct, as a result, we feel the surface we have developed could have a wide range of applications in the biomedical field.
Open Access
Dynamics of protein interactions with new biomimetic interfaces: toward blood-compatible biomaterials
(Colorado State University. Libraries, 2019) Hedayati, Mohammadhasan, author; Kipper, Matt J., advisor; Krapf, Diego, committee member; Reynolds, Melissa, committee member; Bailey, Travis, committee member
Nonspecific blood protein adsorption on the surfaces is the first event that occurs within seconds when a biomaterial comes into contact with blood. This phenomenon may ultimately lead to significant adverse biological responses. Therefore, preventing blood protein adsorption on biomaterial surfaces is a prerequisite towards designing blood-compatible artificial surfaces.
Open Access
Fabrication of slippery textured and slippery non-textured surfaces
(Colorado State University. Libraries, 2018) Cackovic, Matthew, author; Kota, Arun K., advisor; Popat, Ketul, committee member; Bailey, Travis, committee member
Slippery surfaces, i.e., surfaces that have high droplet mobility and low lateral adhesion for liquid droplets, have a wide range of application such as condensation heat transfer, anti-corrosion, lab-on-chip devices, etc. These surfaces can be categorized into smooth slippery surfaces and super-repellant textured slippery surfaces. In this work, we fabricated super-repellant textured superomniphobic paper surfaces. We developed a simple and facile method to fabricate superomniphobic paper surface by growing silicone nanofilaments on a glass microfiber paper surface before imparting low solid surface energy to give the surface the appropriate texture and chemistry. We characterized the performance of our surface and demonstrated our surfaces potential as a lab-on-chip type device. We showed high droplet transport rate, created a simple on-paper pH sensor, demonstrated weight bearing, and showed separation of water from ultra-low surface tension hexane demonstrating the utility of our superomniphobic paper surfaces. We also fabricated a smooth slippery copper surface by creating a chemically and physically homogenous surface. We developed a quick screening test to evaluate the performance of our surfaces in addition to the traditional tests. We showed smoother surfaces performed better and were more slippery.
Open Access
GPU-accelerated computational study of block copolymer self-assembly with advanced polymer theories
(Colorado State University. Libraries, 2024) He, Juntong, author; Wang, Qiang, advisor; Prasad, Ashok, committee member; Bailey, Travis, committee member; Gelfand, Martin, committee member
A high-performance GPU-accelerated software package for self-consistent field (SCF) calculations of block copolymer assembly, PSCF+, has been developed. PSCF+ allows various combinations of chain-connectivity models (including the continuous Gaussian chains, discrete Gaussian chains, and freely jointed chains), non-bonded isotropic pair (including the Dirac δ-function, soft-sphere, dissipative particle dynamics, and Gaussian) potentials and system compressibility (incompressible vs. compressible). The Richardson-extrapolated pseudo-spectral methods, the crystallographic fast Fourier transform, the "slice" algorithm, and the automated calculation-along-a-path are implemented in PSCF+, which not only speed up the SCF calculations and reduce the GPU memory usage significantly, but also make it very efficient in constructing phase diagrams. Given the wide use and great success of SCF calculations in understanding and predicting the self-assembled structures of block copolymer, PSCF+ will be an invaluable computational tool for the polymer community. Using PSCF+, we studied the stability of various Frank-Kasper phases formed by neat diblock copolymer (DBC) A-B melts using the "standard" model and the dissipative particle dynamics chain model and found that in general the SCF phase diagrams of these two models are qualitatively the same but with important differences. We also studied the stability of various Frank-Kasper phases formed by binary DBC blends using the "standard" model and found that the relative stability among the Frank-Kasper phases is dominated by their internal-energy densities. Finally, we performed high-accuracy SCF calculations to study the stability of all known tiling patterns formed by symmetrically interacting ABC miktoarm star triblock terpolymers.
Open Access
Investigation of adipose-derived mesenchymal stem cells interaction with electrospun demineralized bone matrix nanofiber scaffolds
(Colorado State University. Libraries, 2016) Yaprak Akgul, Selin, author; Kipper, Matt, advisor; Popat, Ketul, advisor; Bailey, Travis, committee member; Ehrhart, Nicole, committee member
Nanofiber demineralized bone matrix (DBM) scaffolds were fabricated by electrospinning, and their ability to support cell adhesion and cell viability of murine adipose-derived mesenchymal stem cells (AD-MSCs) for short-term in culture media was investigated. Poly (ε-caprolactone) (PCL) scaffolds were used as control surfaces. Live cell stain calcein-AM and CellTiter 96® Non-Radioactive Cell Proliferation assays were used for cell adhesion and cell proliferation, respectively. DBM scaffolds supported greater cell adhesion compared to PCL nanofiber scaffolds. For cell viability, the two types of scaffolds behaved similarly. The results led to further research on DBM scaffolds. The ability to support osteoblastic differentiation of AD-MSCs for long-term (three weeks) in osteogenic differentiation media was also investigated. Both PCL scaffolds and DBM scaffolds seeded with no cells were used as control surfaces. The total protein content of viable AD-MSCs on the scaffolds was assessed by bicinchoninic acid (BCA) assay. Nanofiber scaffolds displayed increased levels of alkaline phosphatase (ALP) activity for the first week for all cases. ALP activity dropped after one week. Scanning electron microscopy (SEM) and alizarin calcium staining techniques were used to examine mineralization patterns qualitatively on DBM and PCL nanofiber scaffolds. DBM scaffolds deposited more calcium mineral than PCL scaffolds during three-week experiments. Mineralization was quantified by energy-dispersive X-ray spectroscope (EDS). After three weeks of culture, EDS revealed high calcium and phosphorus deposition on DBM scaffolds compared to PCL controls. The DBM scaffolds exhibited increased mineralization over three weeks, both with and without cells. These results demonstrate that the adhesion, proliferation, and osteogenic differentiation of AD-MSCs were influenced by DBM scaffolds.
Open Access
Novel applications of advanced integral-equation theories to various polymeric systems
(Colorado State University. Libraries, 2021) Wang, Yan, author; Wang, Qiang, advisor; Snow, Christopher, committee member; Bailey, Travis, committee member; Grzegorz, Szamel, committee member
To view the abstract, please see the full text of the document.
Open Access
Novel fouling resistant magnetically-responsive membranes for treatment of impaired water
(Colorado State University. Libraries, 2012) Himstedt, Heath Henry, author; Wickramasinghe, S. Ranil, advisor; Bailey, Travis, committee member; Qian, Xianghong, committee member; Ulbricht, Mathias, committee member; Waskom, Reagan, committee member
The focus of this dissertation research is the development of novel fouling resistant magnetically-responsive micromixing filtration membranes. Maintenance and replacement costs account for well over half the total cost of membrane processes. Fouling limits membrane performance by reducing membrane flux and lifetime. Specialized stimuli-responsive membranes have been investigated as a means to combat fouling; however, stimuli such as pH, solution ionic strength, and temperature require changes to the entire feedstream to impart a response. This is time consuming and expensive. The novel membranes presented in this dissertation combat fouling through active hydrodynamic disruption of the filtration boundary layer via instant activation by an external magnetic field without the need to adjust feedstream conditions. The fouling resistant properties of these membranes were tested by using them to treat oily wastewaters from oil and gas production, known as produced water. Chapter 1 introduces concepts referenced throughout the dissertation narrative including basic principles of pressure-driven membrane technology; the principles of membrane fouling and fouling resistant membranes; a review of applications of (super)paramagnetic nanoparticles; and a discussion of produced water and the treatment challenges it presents. Chapters 2 through 6 are published, or soon to be submitted, scientific papers which chronicle the development and application of these novel membranes. Chapter 2 discusses the concepts behind magnetically-activated micromixing and presents initial proof-of-concept nanofiltraiton membranes. Chapter 3 employs track-etched membranes to characterize the modification protocol and the magnitude of the magnetic response, as well as the relationship between the two. Chapter 4 determines the effect of modification grafting density on mixing efficacy and membrane filtration properties. Chapter 5 shows the improvements to membrane performance and lifetime attributable to magnetically-activated mixing during filtration of model produced water and realistic produced water. Chapter 6 builds upon Chapter 5 by using treated realistic produced water permeate as irrigation water. Chapters 7 and 8 summarize the research findings and present possible direction for future research, respectively. This work presents the development and one potential application of novel magnetically-activated micromixing membranes. These membranes reduce membrane fouling by inducing hydrodynamic mixing in an alternating magnetic field. These membranes could lead to improved membrane performance and lifetime when treating highly fouling feedstreams. This would significantly decrease membrane maintenance and replacement costs and could lead to new clean water product streams.
Open Access
Theories and simulations of polymers using coarse-grained models
(Colorado State University. Libraries, 2014) Yang, Delian, author; Wang, David (Qiang), advisor; Bailey, Travis, committee member; Prasad, Ashok, committee member; Szamel, Grzegorz, committee member
Full atomistic simulations of many-chain systems such as polymer melts are not feasible at present due to their formidable computational requirements. Molecular simulations with coarse-grained (CG) models have to be used instead, which interact with soft potentials that allow complete particle overlapping. One advantage of soft potentials is that it allows to simulate systems with experimentally accessible fluctuations and correlations because the invariant degree of polymerization (controlling the system fluctuations and correlations) and the polymer chain length N are decoupled using soft potentials. Another advantage is that it provides a powerful means for unambiguously and quantitatively revealing the effects of fluctuations and correlations of polymers when comparing simulation results with corresponding theoretical predictions based on the same model systems thus without any parameter fitting. Using the recently proposed fast lattice Monte Carlo (FLMC) simulations and the corresponding lattice self-consistent field (LSCF) calculations based on the same model system, where multiple occupancy of lattice sites is allowed, we studied the coil-globule transition (CGT) of one-mushroom polymeric systems and the fused-separated transition (FST) of two-mushroom polymeric systems. With soft potential, we systematically constructed the phase diagrams of one- and two-mushroom systems using LSCF theory, which neglects the interchain fluctuations and correlations. The LSCF predictions were then directly compared with the simulation results without any parameter-fitting, the fluctuation/correlation effects on these phase transitions are then unambiguously quantified. Similarly, for disordered symmetric diblock copolymers in continuum, we directly compared the thermodynamic and structural properties from fast off-lattice Monte Carlo simulations, integral equation (IE) theories (including the reference interaction site model and polymer reference interaction site model), and Gaussian fluctuation theory based on the same model systems, and unambiguously quantified the consequences of various theoretical approximations and the validity of these theories in describing the fluctuations/correlations in disordered diblock copolymers. In order to answer the questions of how to obtain the CG model and how the CG level affects the properties of CG model, we then performed systematic and simulation-free coarse graining of homopolymer melts. In this work, we proposed a systematic and simulation-free strategy for structure-based coarse graining of homopolymer melts, where each chain of Nm monomers is uniformly divided into N segments, with the spatial position of each segment corresponding to the center-of-mass of its monomers. We used integral-equation theories, instead of molecular simulations, to obtain the structural and thermodynamic properties of both original and CG systems, and quantitatively examined how the effective pair potentials between CG segments and the thermodynamic properties of CG systems vary with N. Our coarse-graining strategy is much faster than those using molecular simulations and provides the quantitative basis for choosing the appropriate N-values. Taking the simple hard-core Gaussian thread model (K. S. Schweizer and J. G. Curro, Chem. Phys. 149, 105 (1990)) as the original system, we demonstrated our strategy and compared in detail the various integral-equation theories and closures for coarse graining. Our numerical results showed that the effective CG potentials using various closures can be collapsed approximately onto the same curve for different N, and that structure-based coarse graining cannot give the thermodynamic consistency between original and CG systems at any N < Nm. The CG potential from structure-based coarse graining can further be used to parameterize CG potentials with a given analytic functional form containing finite number of parameters, which is much more convenient to use in molecular simulations than the numerically tabulated CG potentials from structure-based coarse graining. In this work, we applied our systematic and simulation-free strategy to the recently proposed relative-entropy-based coarse graining, which minimizes the information loss quantified by the relative entropy. The values of relative entropy obtained from relative-entropy-based coarse graining with different CG potential functional forms can further be compared to determine the appropriate functional form or number of parameters. Note that the ideal-chain conformations were used in both structure-based and relative-entropy-based coarse-graining strategies, which is not valid for systems with strong pair interactions or small invariant degree of polymerization, self-consistent integral equation theory can be used to obtain more accurate intrachain pair correlations. In order to improve the quality of coarse graining, our proposed systematic and simulation-free coarse-graining strategy can be further combined with the self-consistent integral equation theory. This work will be remained for future researchers.

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