Fischell Department of Bioengineering Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/6628
Browse
157 results
Search Results
Item Hinge-Bill Orientation Techniques for Automated Oyster Processing(1977) Gird, John; Wheaton, F.W.; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, MD)The width and thickness dimensions of oysters and an inclined V-shaped trough were studied as means for achieving end orientation. Two series of experiments were conducted on 2,430 oysters sampled from three different locations in the Chesapeake Bay. Both width and thickness were measured every 0.2 inch along the oyster length from the hinge to the bill end. A width to thickness ratio was found to be the best dimensional combination for distinguishing between the hinge and bill ends. Less than 0.50 percent of all oysters failed the ratio test conditions. Statistical analysis on five width to thickness ratio tests with failure rates between 0.25 and 0.49 percent showed there to be no differences in the percent oyster failure over all bars and across all tests. Results indicate that comparable oyster orienting efficiencies can be attained by width to thickness ratios with orienting points located 0.4 to 1.0 inches in from the oyster ends. Negative results occurred when an inclined V-shaped trough was used for orienting oysters. There were significant differences in the proportion of hinge and bill leading oysters exiting the trough for each trough loading position over all bars and oyster axes. The tendency for the oyster axes to behave differently explained some of the differences in the trough's orienting efficiency. However, there were no significant relationships between orienting efficiency and oyster axes.Item ENGINEERING THE LYMPH NODE MICROENVIRONMENT TO MODULATE ANTIGEN-SPECIFIC T CELL RESPONSE(2019) Gammon, Joshua Marvin; Jewell, Christopher M; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Vaccines and immunotherapies have provided enormous benefit to human health. However, the development of effective vaccines and immunotherapies for many diseases is hindered by challenges created by the complex pathologies of these targets. For example, in cancer the tumor microenvironment suppresses the function of tumor-specific T cells. In autoimmune diseases, lymphocytes specific for self-antigens attack self-tissue. New technologies providing more sophisticated control over immune response are needed to address these challenges. Lymph nodes (LNs) are tissues where adaptive immune responses develop. Therefore, local delivery of combinations of immune signals is a potential strategy to modulate antigen-specific T cell response for pro-immune or regulatory function. However, application of this idea is hindered since traditional administration routes provide little control over the kinetics, combinations and concentrations with which immune signals are delivered to LNs. Biomaterials have emerged as important tools to overcome these challenges as they provide unique capabilities, including co-delivery, targeting, and controlled release. The research presented here harnesses biomaterials to control immune signals present in LNs to modulate antigen-specific T cell response. In one area, intra-LN injection (i.LN) was used to deposit microparticles (MPs) encapsulating tumor-antigens, adjuvants and immunomodulators to promote tumor-specific central memory T cells. These cells display increased proliferative capacity and resistance to tumor-mediated immunosuppression. MPs encapsulating CpG, an inflammatory adjuvant, and a melanoma antigen potently expanded tumor-specific T cells. MPs delivering low doses of rapamycin – a regulatory immune signal – promoted tumor-specific central memory T cells when co-delivered with the melanoma vaccine. Another important aspect of T cell phenotype which can be modulated for therapeutic benefit is regulatory immune response to control autoimmunity. In this second area, biomaterial-based strategies were used to deliver regulatory immune signals to expand regulatory T cells (TREG) and promote immune tolerance. In one direction, liposomes were designed to deliver regulatory metabolic modulators to bias T cells. In a parallel direction, MPs encapsulating rapamycin and islet self-antigens were designed to promote tolerance in T1D. i.LN delivery of MPs expanded islet-specific TREG and inhibited disease in a mouse model of T1D. Together this work demonstrates potent and modular strategies to therapeutically modulate T cell response.Item SPRAYABLE, BIODEGRADABLE POLYMER BLENDS FOR TISSUE ADHESION(2019) Daristotle, John L; Kofinas, Peter; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Tissue adhesive materials can revolutionize surgical procedures, but they are often difficult to apply safely because of a required curing step where the viscous components of a glue solidify and become sticky. To simplify their deposition and improve their usability, this dissertation introduces tissue adhesive polymer blends that can be sprayed using a fiber production technique called solution blow spinning. The polymer blends studied here are innovative because they are non-curing: the polymer accumulates as a solid material directly on the tissue substrate of interest during spraying, quickly forming a strong bond. To achieve a rapid increase in tissue adhesion, we developed a surgical sealant composed of poly(lactic-co-glycolic acid) and poly(ethylene glycol) (PLGA/PEG) that becomes adhesive in response to warming to body temperature. We then evaluated PLGA/PEG in small and large animal models of intestinal anastomosis and partial thickness skin wounds. Additional improvements to hemostasis, flexibility, and adhesion were made by incorporating micron-sized silica particles, which produced textured fibers with suppressed crack formation. We also developed the first pressure-sensitive tissue adhesive by formulating elastomeric copolymer blends with two components of different molecular weights. An additional objective of this dissertation was to study sprayable polymers that can be used as a controlled release system for various drugs. Towards this goal, we incorporated antimicrobial silver into solution blow spun PLGA/PEG fibers. At the optimal concentration, silver ions released over 14 days at levels that were effectively antimicrobial with minimal cytotoxicity. Coating strategies for controlling the delivery of polyelectrolyte complexes were also investigated.Item Quantitative Phenotyping of Brain Endothelial Cell-Cell Junctions for Physiological and Pathophysiological Applications(2019) Gray, Kelsey M; Stroka, Kimberly M; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The integrity of endothelial cell-cell junctions is required for the maintenance of normal physiological processes. The expression of junctional proteins is particularly important in the endothelial cells of the blood-brain barrier (BBB), the cellular unit that protects the brain via regulated transport between the peripheral blood and the central nervous system. Dysfunction of the BBB is linked with decreased junctional protein localization and is implicated in several diseases including Alzheimer’s disease and multiple sclerosis. On the other hand, the tight junctions of the BBB impede the delivery of medications targeting the brain. Therefore, understanding the key players driving junction stability could hold significant promise for therapeutic discovery and drug delivery applications. Despite this, the mechanisms underlying junction disruption aren’t fully understood. While several studies have linked different junction protein patterns with altered barrier function, the quantification of this parameter remains limited due to the lack of efficient measurement techniques. Here, we aimed to investigate the influence of junction phenotype on brain endothelial barrier properties. To accomplish this, we developed the Junction Analyzer Program (JAnaP) to semi-automatically calculate edge-localization protein phenotypes. Application of the JAnaP to measure the junctional proteins VE-cadherin and ZO-1 in different physiological and pathophysiological conditions revealed that discontinuous junctions contribute more to barrier permeability compared to continuous, linear junctions. Continuous junctions were also increased in endothelial cells with decreased contractility, mediated biochemically or by lowered subendothelial matrix stiffness. Finally, breast cancer cell secreted factors increased immature adherens junctions, likely through VEGF signaling, but minimally affected tight junction presentation. Thus far, the development and application of the JAnaP has revealed insights into the effects of junction patterns on barrier function, the mechanobiology of endothelial cells, and the response of brain endothelial cells to biochemical cues involved in breast cancer metastasis. Understanding the conditions driving altered junction presentation, and the resultant effects on barrier integrity, could lead to the development of therapeutics capable of traversing the BBB for delivery to the brain or for diseases associated with BBB dysfunction. Future use of this program holds significant potential for physiological and pathophysiological study in various endothelial and epithelial cell systems.Item Strategies to enhance the stability and potency of extracellular vesicle therapeutics(2019) Jeyaram, Anjana; Jay, Steven M; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As key mediators of intercellular communication, extracellular vesicles (EVs) have emerged as a new therapeutic modality, specifically via a microRNA (miRNA) transfer mechanism. Unlike synthetic carriers and liposomes, EVs can evade endosomal degradation, show low immunogenicity, and are able to cross biological barriers. Despite the advantages of using EVs as therapeutic carriers, there remain several obstacles to clinical translation. Intrinsic RNA levels in EVs are low and current exogenous loading methods are inefficient and may damage EVs or their nucleic acid cargo, which can ultimately impair bioactivity. Even if the therapeutic cargo can be loaded effectively, the stability of these formulations must be evaluated and improved to preserve potency after storage for use in clinical settings. Thus, we hypothesize that studying and developing new methods to load and store EVs can enhance our understanding of EVs and improve the delivery of nucleic acid cargo. Here, we develop two techniques for loading nucleic acid cargo into extracellular vesicles and assess the impact of different storage conditions on EV stability. Sonication was shown to be a viable method for cargo loading without inducing cargo and vesicle aggregation. Next, the stability of both endogenously therapeutic EVs and those loaded with cargo via sonication was assessed. -80°C storage preserved EV activity and -20°C or lyophilized EVs stored at room temperature were shown to be comparable. However, EVs loaded via sonication saw a loss in cargo retention within a week of storage. Lastly, we developed a novel method for loading based on the creation of a pH-gradient within EVs. This allowed for enhanced passive incorporation of negatively charged cargo into vesicles without perturbing the membrane. Collectively, the work in this dissertation improves our understanding of the methods used to preserve and enhance the potency of extracellular vesicle therapeutics. This information provides new knowledge on the nature of EVs and their durability, enhancing their potential as an important delivery vehicle.Item DEVELOPMENT OF AN INTEGRATED CAPSULE SYSTEM FOR GASTROINTESTINAL-TARGETED BIOSENSING(2019) Banis, George Efstratios; Ghodssi, Reza; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Non-invasive microsystems are emerging as a means to address diagnostics challenges in healthcare due to the potential to retrieve information at the source and in a personalized approach. The gastrointestinal (GI) tract is a hub of information that alters in composition during both homeostatic and pathological conditions, and often manifests as varying biochemical concentrations in cell and tissue-sourced secretions. Thus, innovative strategies to sample molecular information from these secretions would be of significant benefit to physicians in establishing an appropriate prognosis. This dissertation describes the development of a film-based capacitive sensing strategy and subsequent integration into a capsule-based microsystem that is designed to travel through the GI tract upon ingestion until it passes through the stomach, where it is designed to measure model analytes in duodenal secretions. Subsequently, the measurements are processed into signals for wireless transmission, enabling external analysis for potential clinical utility. To achieve a system that can be safely ingested by patients, design features must be implemented that follow previously established standards in device requirements such as geometry and biocompatibility. In this work, I aid in the design, integration, and characterization of a capsule-embedded sensing system using commercial off-the-shelf components that interface capacitive transducers (range: 0.8-220 pF; sensitivity: 7.3x10-3) with a smart phone via Bluetooth Low Energy (2.4 GHz). The transducers are designed to measure the change in dielectric constant of interfacing media, which transitions when specific environmental (pH) characteristics are met. The system, including the power supply, are manufactured on a printed circuit board and packaged within a 3D-printed capsule structure (13 mm x 35 mm) that maintains dimensions of other clinically utilized ingestible capsule devices. The system is cost effective, user-friendly, biocompatible, and can serve as a highly customizable platform for measuring a variety of desired targets. Secretions from various GI organs can be distinguished by pH, as is demonstrated in the pharmaceutical industry via enteric coatings that dissolve in target pH ranges but maintain structural stability in others. I employ such coatings for protecting our system until targeting the pH, and therefore GI region, of interest for sampling. Once dissolved, microfluidic inlets allow access for the media to interface with the sensors. I studied coatings that respond to both acidic (pH 6), as well as pH sequences via hierarchical coatings. Because the target analytes react with naturally occurring substrates, I investigate label-free sensing of model enzymes such as pancreatic trypsin (20-40 μM) and lipase (10 μM-1 mM), as well as bile salts (0.07-7 %w/v) as a model emulsifier, using films composed of biomaterials, including gelatin and stearin. To integrate these materials with the desired microsystem, I investigate various film deposition and modification strategies. Studies performed with our platform suggest the potential for the ability to sample the target fluid, as well as sense the analyte of interest in different concentrations by comparing the rate of capacitance change upon fluid entry compared to uncoated controls. Using this system, I characterize its potential for utility as a non-invasive platform for targeting multiple GI regions and detecting sensor-compatible biomarkers.Item ENABLING RAPID PHENOTYPIC DETECTION OF CEPHALOSPORIN RESISTANCE BEYOND THE CENTRAL LABORATORY(2019) Nguyen, Hieu Thuong; White, Ian; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The so-called bacterial “superbugs” are largely resistant to some of the most commonly prescribed antibiotics, including a drug class known as cephalosporins used to treat many hospital and community-acquired infections. This major public health threat has been acknowledged for decades by the Centers for Disease Control (CDC) as a major concern; yet, the detection of superbugs has not been made routine since standard testing practices have been limited to specialized “central” laboratories with sophisticated yet bulky and expensive equipment and highly trained personnel. As a result, the lack of simpler testing methods that can be used in everyday clinics and doctor’s offices can be viewed as a source of error contributing to incorrect antibiotic treatment and poorer patient outcomes, factors that drive even more advanced resistance, depleting our drugs or last resort. In this dissertation, we explore new strategies for simplified methods to test for cephalosporin resistance in order to give higher accessibility in the timely detection of superbugs to support the improvement of patient care. To do this, we take an organic chemistry and biochemical approach to develop new detection molecules that report resistance activity in bacteria expressing extended-spectrum β-lactamase (ESBL) enzymes, one of the most prolific resistance strategies used by superbugs. Next, we describe methods of integrating these detection molecules into practical testing methods, and detail the engineering of simpler assays that allow for rapid readout of ESBL phenotypes using commonplace laboratory plate readers, portable Raman devices, and even handheld personal glucose meters (used for diabetes monitoring) purchased from the drugstore.Item Techniques and Applications of Mesoscopic Fluorescence Imaging(2019) Liu, Yi; Chen, Yu; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)There is increasing interest towards visualization of tissue level with deep penetration depth in bioscience and medical research, mesoscopic imaging exchanges resolution for penetration depth, which offers hundreds of micrometer resolution and up to several millimeter penetration depth. By introducing fluorescence dyes or with intrinsic fluorescence, much higher contrast of images can be recorded compared to reflection imaging. To assess the characteristics of fluorescence imaging system, in the first part of this thesis I will discuss 3D printing technique as a novel phantom fabrication method which enables the fabrication of optically realistic and morphologically complex tissue-simulating phantoms for the development and evaluation of optical imaging products. In the second part, I will discuss about the techniques and applications of Angled fluorescence laminar optical tomography (aFLOT), a modified fluorescence tomographic imaging technique based on 3D reconstructions. To extend the capability of aFLOT to acquire more bioinformation besides, its availability for quantification and statistics has been studied. Some technical improvements of aFLOT system performance has also been taken by incorporating algorithms for imaging processing. In addition, examples of biomedical applications have been discussed to demonstrate the capability of aFLOT system in both bioscience and medical research field.Item Dual-Chambered Membrane Bioreactor for the Dynamic Co-Culture of Dermal Stratified Tissues(2019) Navarro Rueda, Javier; Fisher, John P; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Every year over 11 million patients suffer severe burns worldwide. Facial burn statistics include victims of violence (warfare, acid attacks, scalding) and trauma (flame, electrical, chemical). Skin is the first barrier against external mechanical and biochemical factors, such as burning agents, and is composed of the epidermis, dermis, and hypodermis layers. When burned, skin cannot regulate temperature or fluid transport, or stop bacterial infection. Due to the importance of the skin barrier, natural healing and grafting treatments aim to quickly close the wounds with fast proliferation of fibroblasts and collagen deposition, a process that results in scarring, loss of function, and disfigurement. Tissue engineering has produced epidermis-dermis skin scaffolds for clinical use and in vitro dermal models. Throughout this work we studied 3D printing and bioreactor strategies for the simultaneous physiologic and topographic reconstruction of burnt facial skin tissues. First, we formulated a keratin-based bioink that can be used for 3D printing on a lithography-based 3D printer. Second, we implemented the keratin bioink in the production of Halofuginone-laden face masks for the improvement of contracture, scarring, and aesthetics in severe skin wound healing in an animal model. Due to lack of collagen organization and microstructural development, we introduced a novel dual-chambered (DCB) bioreactor system to study stratified tissues. For this, crosslinking density of the keratin-based hydrogels was used to fine tune the transport properties of membranes for potential use in guided tissue regeneration applications. Then, we assessed the viability of our novel DCB for co-culturing adjacent cell populations with the inclusion of a regulatory keratin membrane. Last, having studied the DCB with flat interfaces, we assessed its viability for perfusing curved interfaces. The integration of both curvature and cell populations allowed to assess the synergistic development of adjacent dermis fibroblasts and hypodermis stem-cell-derived adipocytes and evaluate whether including topography parameters would alter cell viability in the DCB. The strategies developed here elucidate on tissue stratification and aesthetic reconstruction. Furthermore, the keratin-based bioink, the engineered membranes, and the DCBs can be extended to study other stratified or gradient tissues and to fine-tune communication between cell populations in complex 3D constructs.Item Colloid Assembly Strategies For Structurally Colored Materials And Protease Detection(2019) Torres, Leopoldo; Kofinas, Peter; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The goal of this dissertation is to better understand a mechanism that produces large color changes in a protease responsive nanoparticle hydrogel (PRNH) with structural color. The outcomes of this research can lead in the development of a peptide-based hydrogel optical sensor for the detection of toxic proteases in solution to prevent public exposure by means of water or food source contamination, and a potential terrorist event. Towards this application, a structural color changing SiO2 nanoparticle hydrogel film was made with a 4-arm poly(ethylene glycol) terminated with carboxylic acid norbornene (4PEGN), and a degradable dicysteine peptide. To fabricate the PRNHs, a rapid and tunable centrifugation-based assembly was developed. The color of centrifuged colloids of a single particle diameter was precisely controlled within 50 nm by modulating the particle concentration. The peak wavelength reflected by the material was further tuned by altering the centrifugal rate and assembly time. When placed in a protease solution, the peptide crosslinks degrade causing electrostatic binding and adsorption of the polymer to the particle surface which leads to the assembly of particles into compact amorphous arrays with structural color. Only PRNHs with highly negative particle surface charge exhibit color changes after degradation. Ultra-small angle x-ray scattering revealed that the particles become coated in polymer after degradation, producing a material with less order compared to the initial state. Altering the particle diameter modulates the composites' color, and all sizes investigated (178–297 nm) undergo the degradation-directed assembly. Varying the amount of 4PEGN adjusts the swollen PRNH color and has no effect on the degradation-directed assembly. Next, a botulinum neurotoxin (Botox) responsive nanoparticle hydrogel was developed. Its stability, optical properties, and response time were characterized and optimized for detecting 10 µg/mL of BoTox in solution. Last, a new method to produce bright full-spectrum structurally colored fluids that are non-iridescent is presented. The color was modulated by altering the particle volume fraction and a model predicting the peak wavelength reflected by the colloid was developed. Collectively, this body of work advances the development of responsive structurally colored detection platforms and particle assembly strategies for the production of structural color.