Engineering Commons^™

Development Of Collagen-Based Scaffolds For Differentiation Of Induced Pluripotent Stem Cells, Siteng Fang

Graduate Dissertations and Theses

Collagen hydrogel has been broadly studied and applied in engineering 3D scaffold materials in tissue engineering. A collagen hydrogel can provide cells with a porous and soft environment to proliferate and differentiate. However, lacking mechanical stiffness and shrinkage resistance made it a challenge to sustain shape and size during a long stem cell differentiation process. In addition, a cytocompatible scaffold for human induced pluripotent stem cell (iPSC)-laden culture has not been fully investigated. The goal of this study is to develop stable and biocompatible collagen-based scaffolds that are suitable for direct seeding and lineage progression of iPSCs. In this work, …

Fibers For Skin Regeneration, Astrid Michelle Rodriguez Negron

Theses and Dissertations

This thesis presents the successful development of biocompatible Polyvinyl Butyral (PVB), PVB/Polylysine and PVB/Tannic Acid (TA)/Polylysine fibers from an ethanol solution, Polyhydroxybutyrate (PHB), PHB/Polylysine, PHB/TA/Polylysine fibers from a chloroform solution and Chitosan (CH)/Pullulan (PL)/TA and CH/PL/TA/Polylysine fibers from an aqueous solution. The fibers were mass produced utilizing the Forcespinning® (FS) technology. The morphology of the fibers was characterized using a scanning electron microscope (SEM) and the fibers average diameter was calculated. The thermal properties of the fibers were characterized using a thermogravimetric analyzer (TGA) and a differential scanning calorimeter (DSC). The antibacterial activity of the fibers was assessed using against …

Understanding The Surface Fouling Mechanism Of Ultrananocrystalline Diamond Microelectrodes Using Microfluidics For Neurochemical Detection, An-Yi Chang

Doctoral Dissertations

Electrochemical methods are widely used for chronic neurochemical sensing, but thus far, the organic solution redox reactions fouled the electrodes' surface. It caused the reduction of sensitivity and the electrodes' lifetime.

Here, we present the boron-doped nanocrystalline diamond microelectrodes (BDUNCD) as the next generation electrode material for neurochemical sensor development. To aid in long-term chronic monitoring of neurochemicals, they have a wide window of electrochemical potential, extremely low background current, and excellent chemical inertness. The main research goal is to reduce the rate of electrode fouling due to the reaction by-products, and significantly extend their useful lifetime.

We systematically characterize …

Sensitivity Of Diffuse Reflectance Spectroscopy To Dose- And Depth-Dependent Changes In Tumor Oxygenation After Radiation Therapy, Daria Semeniak

Graduate Theses and Dissertations

Along with chemotherapy, immunotherapy, and surgery, radiotherapy is one of the most common treatments used against cancer. Around 50% of all cancer patients undergo radiation therapy. While for some patients radiotherapy works efficiently and lead to a complete cancer disappearance, for others treatment outcome may be less favorable due to radioresistance processes happening within a tumor on the molecular level. Radioresistance remains a big challenge for modern oncology. The ability to identify radioresistance at the early stage of radiotherapy would help physicians to improve therapy efficiency. At the current moment, despite the rapid progress in cancer understanding and diagnostic modalities, …

Improvement Of Fluorescence-Based Microfluidic Dna Analyzers, Collin Tranter

Doctoral Dissertations

A tremendous effort continues in the development of micro-total-analysis-systems; in support of this, many chemical passivation methods have been developed to enhance the biocompatibility of such microfluidic systems. However, the suitability of these passivation techniques to many fluorescence-based assays still remains inconsistent. This part of this work is focused on the performance of a third generation intercalating DNA dye when used within microfluidic devices treated with a select variety of passivating coatings. The results of these tests indicate that passivation coatings which are intended to shed DNA based on electrostatic repulsion will in fact imbibe the fluorescent DNA intercalating dye …

Development Of A Nonlinear Model For The Prediction Of Response Times Of Glucose Affinity Sensors Using Concanavalin A And Dextran And The Development Of A Differential Osmotic Glucose Affinity Sensor, Louis G. Reis

Doctoral Dissertations

With the increasing prevalence of diabetes in the United States and worldwide, blood glucose monitoring must be accurate and reliable. Current enzymatic sensors have numerous disadvantages that make them unreliable and unfavorable among patients. Recent research in glucose affinity sensors correct some of the problems that enzymatic sensors experience. Dextran and concanavalin A are two of the more common components used in glucose affinity sensors. When these sensors were first explored, a model was derived to predict the response time of a glucose affinity sensor using concanavalin A and dextran. However, the model assumed the system was linear and fell …

Expanding The Applications Of Poly(Dimethylsiloxane) In Biomicrofluidics, Sawyer D. Stone

Doctoral Dissertations

This work aims to create novel applications for poly(dimethylsiloxane) (PDMS) in the field of biomicrofluidics through oxidative stress detection, doping of the polymer for intentional leaching into microdevices, and the development of low-cost implements for fabricating PDMS microfluidic devices. PDMS has become the polymer of choice for research in microfluidics due to its optical clarity, ease of fabrication, flexibility in design, good mechanical properties, and the ability to chemically modify the surface.

Biomicrofluidics enables the rapid throughput and analysis of small biological samples requiring less time investment and reagent use than traditional macroscale laboratory techniques. Polymer devices are inexpensive, easily …

Device Design Factors For Enhancing The Functionality Of Chronic Intracortical Microelectrodes, Heui Chang Lee

Open Access Dissertations

Intracortical microelectrodes are devices used in brain-computer interfaces (BCI) to help regain lost motor, sensory, and cognitive functions of individuals with neurological disorders. However, the long-term performance of microelectrode arrays is hampered by a series of inflammatory tissue responses. The consequence of the inflammatory response is the formation of a dense astroglial sheath around the vicinity of the electrode, impeding the electrical conduction between the electrode and neurons. Furthermore, due to the cascade of neuroinflammatory events, the number of neurons is significantly reduced near the electrode, manifested by decrease in signal-to-noise ratio (SNR) and the yield of electrodes. Over time, …

Characterizing The Effects Of Repetitive Head Trauma In Female Soccer Athletes For Prevention Of Mild Traumatic Brain Injury, Diana Otero Svaldi

Open Access Dissertations

As participation in women’s soccer continues to grow and the longevity of female athletes’ careers continues to increase, prevention of mTBI in women’s soccer has become a major concern for female athletes as the long-term risks associated with a history of mTBI are well documented. Among women’s sports, soccer exhibits the highest concussion rates, on par with those of men’s football at the collegiate level. Head impact monitoring technology has revealed that “concussive hits” occurring directly before symptomatic injury are not predictive of mTBI, suggesting that the cumulative effect of repetitive head impacts experienced by collision sport athletes should be …

Dynamic Holography In Semiconductors And Biomedical Optics, Hao Sun

Open Access Dissertations

Three-dimensional scanning and display are rapidly-advancing new technologies with important commercial drivers such as 3D printing and remote imaging for big data applications. Holography is a natural approach to recording and displaying three-dimensional information because it uses phase-sensitive interferometry to record interference patterns when a reference beam encounters coherent light arriving from an object. The 3D information is contained in the values of wave optics. Holography is a broad field that goes beyond recording and displaying. For instance, holographic optical elements, which take advantage of holographic imaging principles, perform the functions of lenses, gratings or mirrors. Holographic interferometry is also …

Mathematical Analysis Of Feedback Targets Of Bmp Signaling In Drosophila Embryonic Development, Yan Luo

Open Access Theses

Bone morphogenetic proteins (BMPs) drive a range of cellular processes especially in the early stages of embryonic development. This family of proteins acts as one of the most important extracellular signals in development pattern formation across the animal kingdom. Cells in embryos differentiate into different cell types in response to the concentration level of BMP. This complex process is regulated by multiple regulators that serve to tune the signal response.

Extensive experimental and computational research has been performed to analyze BMP regulation in Drosophila, a widely studied model organism, and has advanced our understanding of animal development. Because of …

Concurrent Detection And Isolation Of Cellular And Molecular Biomarkers, Wanfeng Huang

Open Access Dissertations

Detection of cancer markers such as protein biomolecules and cancer cells in bodily fluids is of great importance in early diagnosis, prognosis as well as evaluation of therapy efficacy. Numerous devices have been developed for detecting either cellular or molecular targets, however there has not yet been a system that can simultaneously detect both cellular and molecular targets effectively. Molecule and cell-based assays are important because each type of target can tell a different story about the state of the disease and the two types of information can potentially be combined and/or compared for more accurate biological or clinical assessments. …

Laser-Processed Parchment Paper For Fabrication Of Chronic Wound Dressings With Selective Oxygenation, Manuel Ochoa

Open Access Dissertations

Chronic non-healing wounds (e.g., diabetic foot ulcers and bed sores) impact over 6.5 million Americans per year, costs in excess of $25 billion to treat on an annual basis, and are on the rise due to increasing levels of obesity and diabetes compounded by an aging population. A major inhibitor of healing is suboptimal oxygenation of the wound bed. Unlike acute injuries that receive sufficient oxygen via a functional blood vessel network, chronic wounds often suffer from the lack of a proper vascular network; thus being incapable of providing sufficient oxygen for tissue growth. Typical medical treatment of hypoxic chronic …

Scaffold And Tissue Based Therapies To Improve Skeletal Muscle Regeneration After Volumetric Muscle Loss, Benjamin Kasukonis

Graduate Theses and Dissertations

Volumetric muscle loss (VML) is an injury to skeletal muscle characterized by a loss of more than 20% of a muscles volume. The combination of the bulk loss of tissue, transection and separation of myofibers proximal and distal to the injury, loss of innervation and blood supply, and the depletion of muscle progenitor cells results in permanent fibrosis and functional deficits due to loss of contractile tissue. Scaffolds, cells, and engineered constructs have been explored as potential therapeutic interventions to induce myogenesis at the site of a VML injury in animal models, in addition to limited clinical trials. This dissertation …

Examination Of Pseudomonas Fluorescence As A Recombinant Expression Host: Cloning, Expression, And Chromatography, Ahmed K.Ali Elmasheiti

Graduate Theses and Dissertations

In an effort to expand the pool of bacterium useful for biotechnology applications, Pseudomonas fluorescens, a common gram negative microbe, was examined for its ability to function in a recombinant setting. P. fluorescens is ubiquitous in nature and was initially identified as a soil bacterium found in dirt and is typically associated with plant material. Past literature indicates that it shared characteristics common to Escherichia coli and Bacillus subtilis, including simple growth conditions and potential cloning vectors, providing motivation to look into both the upstream and downstream characteristics of this bacterium. First, it was demonstrated that P. fluorescens could be …

A Portable And Automatic Biosensing Instrument For Detection Of Foodborne Pathogenic Bacteria In Food Samples, Zhuo Zhao

Graduate Theses and Dissertations

Foodborne diseases are a growing public health problem. In recent years, many rapid detection methods have been reported, but most of them are still in lab research and not practical for use in the field. In this study, a portable and automatic biosensing instrument was designed and constructed for separation and detection of target pathogens in food samples using nanobead-based magnetic separation and quantum dots (QDs)-labeled fluorescence measurement. The instrument consisted of a laptop with LabVIEW software, a data acquisition card (DAQ), a fluorescent detector, micro-pumps, stepper motors, and 3D printed tube holders. First, a sample in a syringe was …

A Bifunctional Nanocomposites Based Electrochemical Biosensor For In-Field Detection Of Pathogenic Bacteria In Food, Meng Xu

Graduate Theses and Dissertations

This research focused on the application of electrochemical biosensors for the rapid detection of pathogenic bacteria, Escherichia coli O157:H7 and Salmonella Typhimurium, in foods. The possible presence of pathogenic bacteria in foods has always been a great threat to the wellbeing of people and the revenue of food companies. Therefore, the demand for rapid and sensitive methods to detect foodborne pathogens is growing. In this research, an impedimetric immunosensor was first developed for the rapid detection of E. coli O157:H7 and S. Typhimurium in foods. It was based on the techniques of immunomagnetic separation, enzyme labelling, and electrochemical impedance spectroscopy …

Knee Joint Internal Forces During Squat Jump Exercise, Ricardo Moreno

Theses and Dissertations

The purpose of this research is to investigate muscular ligament and joint contact forces produced during squat jump exercise. An inverse dynamics, two dimensional, leg model is used to describe the motion in the sagittal plane. The lower extremity model includes two bones, tibia and femur, tibio-femoral ligaments, and muscles such as quadriceps, hamstrings, and gastrocnemius. The ligaments are anatomically modeled as nonlinear strings, but the femoral condyle is modeled as a circle and the tibial plateau as a straight line. Experimental squat jump exercises are conducted to obtain the ground reaction forces, the angular accelerations, and centroid linear acceleration …

Exploring The Production Of Extracellular Matrix By Astrocytes In Response To Mimetic Traumatic Brain Injury, Addison Walker

Graduate Theses and Dissertations

Following injury to the central nervous system, extracellular modulations are apparent at

the site of injury, often resulting in a glial scar. Astrocytes are mechanosensitive cells, which can create a neuroinhibitory extracellular environment in response to injury. The aim for this research was to gain a fundamental understanding of the affects a diffuse traumatic brain injury has on the astrocyte extracellular environment after injury. To accomplish this, a bioreactor culturing astrocytes in 3D constructs delivered 150G decelerations with 20% biaxial strain to mimic a traumatic brain injury. Experiments were designed to compare the potential effects of media type, number of …

Lab-On-A-Chip Nucleic-Acid Analysis Towards Point-Of-Care Applications, Varun Lingaiah Kopparthy

Doctoral Dissertations

Recent infectious disease outbreaks, such as Ebola in 2013, highlight the need for fast and accurate diagnostic tools to combat the global spread of the disease. Detection and identification of the disease-causing viruses and bacteria at the genetic level is required for accurate diagnosis of the disease. Nucleic acid analysis systems have shown promise in identifying diseases such as HIV, anthrax, and Ebola in the past. Conventional nucleic acid analysis systems are still time consuming, and are not suitable for point-ofcare applications. Miniaturized nucleic acid systems has shown great promise for rapid analysis, but they have not been commercialized due …

Anxiolytic Effects Of Propranolol And Diphenoxylate On Mice And Automated Stretch-Attend Posture Analysis, Kevin Scott Holly

Doctoral Dissertations

The prevention of social anxiety, performance anxiety, and social phobia via the combination of two generic drugs, diphenoxylate HC1 (opioid) plus atropine sulfate (anticholinergic) and propranolol HCl (beta blocker) was evaluated in mice through behavioral studies. A patent published on a September 8, 2011 by Benjamin D. Holly, US 2011/0218215 Al, prompted the research. The drug combination of diphenoxylate and atropine plus propranolol could be an immediate treatment for patients suffering from acute phobic and social anxiety disorders. Demonstrating the anxiolytic effects of the treatment on mice would validate a mouse model for neuroscientist to be used to detect the …

Potential Applications For Halloysite Nanotubes Based Drug Delivery Systems, Lin Sun

Doctoral Dissertations

Drug delivery refers to approaches, formulations, technologies, and systems for transporting a drug in the body. The purpose is to enhance the drug efficacy and to reduce side reactions, which can significantly improve treatment outcomes. Halloysite is a naturally occurred alumino-silicate clay with a tubular structure. It is a biocompatible material with a big surface area which can be used for attachment of targeted molecules. Besides, loaded molecules can present a sustained release manner in solution. These properties make halloysite nanotubes (HNTs) a good option for drug delivery.

In this study, a drug delivery system was built based on halloysite …

Generalized Partial Directed Coherence And Centrality Measures In Brain Networks For Epileptogenic Focus Localization, Joshua Aaron Adkinson

Doctoral Dissertations

Accurate epileptogenic focus localization is required prior to surgical resection of brain tissue for treatment of patients with intractable temporal lobe epilepsy, a clinical need that is partially fulfilled to date through a subjective, and at times inconclusive, evaluation of the recorded electroencephalogram (EEG). Using brain connectivity analysis, patterns of causal interactions between brain regions were derived from multichannel EEG of 127 seizures in nine patients with focal, temporal lobe epilepsy (TLE). The statistically significant directed interactions in the reconstructed brain networks were estimated from three second intracranial multi-electrode EEG segments using the Generalized Partial Directed Coherence (GPDC) and validated …

Optical Dosimetry Tools And Monte Carlo Based Methods For Applications In Image Guided Optical Therapy In The Brain, Akshay N Prabhu Verleker

Open Access Dissertations

Purpose: The long-term goal of this research is to determine the feasibility of using near infra-red light to stimulate drug release in metastatic lesions within the brain. In this work, we focused on developing the tools needed to quantify and verify photon fluence distribution in biological tissue. To accomplish this task, an optical dosimetry probe and Monte Carlo based simulation code were fabricated, calibrated and developed to predict light transport in heterogeneous tissue phantoms of the skull and brain. Empirical model (EM) of photon transport using CT images as input were devised to provide real-time calculations capable of being translated …

The Role Of Mechanical Loading In Chondrocyte Signaling Pathways, Qiaoqiao Wan

Open Access Dissertations

Chondrocytes are a predominant cell type present in articular cartilage, whose integrity is jeopardized in joint degenerative diseases such as osteoarthritis (OA). In the chondrocytes of patients with OA, the elevated levels of inflammatory cytokines such as interleukin 1β (IL1β) and tumor necrosis factor α (TNFα) have been reported. These cytokines contribute to degradation of cartilage matrix by increasing activities of proteolytic enzymes. In addition to their contribution to proteolytic enzymes, these cytokines adversely affect anabolic activity of chondrocytes by inhibiting the production of proteoglycans and type II collagen. Therefore, blocking the action of these cytokines is a potential strategy …

Development Of A Fluidic Mixing Nozzle For 3d Bioprinting, Will Hoggatt

Open Access Theses

3D bioprinting is a relatively new and very promising field that uses conventional 3D printing techniques and adapts them to print biological materials that are suited for use with cells. These bioprinters can be used to print cells encapsulated within biological "ink" (bio-ink) to create and customize complex three-dimensional tissues and organs. Our work has focused on developing a new bioprinter nozzle that addresses critical gaps with present-day bioprinters, namely, the lack of standardized, physiologically-relevant biomaterials, and their one nozzle per composition printing capacity. These shortcomings preclude printing a range of cellular and biomaterial compositions (including gradients of cells and …

Development Of Orthogonally Crosslinked Thiol-Ene Hydrogels For Encapsulation Of Pancreatic Beta-Cells, Han Shih

Open Access Dissertations

Type I diabetes mellitus (T1DM) is an autoimmune disease caused by auto-reactive T-cell-mediated destruction of insulin-producing β-cells. Effective encapsulation strategies can protect the transplanted islets from direct attack by host immune cells while maintaining insulin secretion. To achieve this goal, I have developed a hydrogel conformal coating using a visible light-mediated interfacial thiol-ene photopolymerization. Unlike conventional chain-growth visible light polymerizations, no additional cytotoxic co-initiator or co-monomer was required in thiol-ene gelation scheme for rapid gelation. More importantly, islets coated with thiol-ene gel maintained their viability and function in vitro. In addition to microencapsulate β-cells, the second objective of my …

Chlorine Demand Shows Thresholds And Hierarchy With Source Water Quality At Beaver Lake, Arkansas, Jaime M. Gile

Graduate Theses and Dissertations

This study investigated the effects of source water quality in Beaver Lake on the amount of chlorine (Cl) needed to develop decision support system to help guide chlorination practices in pre-treatment of source water. Chlorine demand assays were performed on water samples from Beaver Lake collected from the intake structure at Beaver Water District from March 2014 through August 2015, and using data from these assays, the two points of interest in this study were the Cl dose at which Cl residuals began to accumulate and the mean Cl demand occurring after that dose. Three methods of analysis were used …

Nano Clay-Enhanced Calcium Phosphate Cements And Hydrogels For Biomedical Applications, Udayabhanu Jammalamadaka

Doctoral Dissertations

Biomaterials are used as templates for drug delivery, scaffolds in tissue engineering, grafts in surgeries, and support for tissue regeneration. Novel biomaterial composites are needed to meet multifaceted requirements of compatibility, ease of fabrication and controlled drug delivery. Currently used biomaterials in orthopedics surgeries suffer limitations in toxicity and preventing infections. Polymethyl methacrylate (PMMA) used as bone cement suffers from limitations of thermal necrosis and monomer toxicity calls for development of better cementing biomaterials. A biodegradable/bioresorbable cement with good mechanical properties is needed to address this short coming. Metal implants used in fixing fractures or total joint replacement needs improvements …

Validation Of A Confocal Light Sheet Microscope Using Push Broom Translation For Biomedical Applications, Joshua Hutcheson

Graduate Theses and Dissertations

There exists a need for research of optical methods capable of image cytometry suitable for point-of-care technology. To propose am optical approach with no moving parts for simplification of mechanical components for the further development of the technology to the poin-of-care, a linear sensor with push broom translation method. Push broom translation is a method of moving objects by the sensor for an extended field of view. A polydimethylsiloxane (PDMS) microfluidic chamber with a syringe pump was used to deliver objects by the sensor. The volumetric rate of the pump was correlated to the integration time of the sensor to …