Chemical and Biomolecular Engineering Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2751
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Item SYNTHESIS AND CHARACTERIZATION OF ENERGETIC NANOMATERIALS WITH TUNABLE REACTIVITY FOR PROPULSION APPLICATIONS(2020) Kline, Dylan Jacob; Zachariah, Michael R.; Liu, Dongxia; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Combustion is the world’s leading energy conversion method in which a fuel and oxidizer react and release energy, typically in the form of heat. Energetic materials (propellants, pyrotechnics, and explosives) have combustion reactions that are so fast that they are generally limited by how quickly the fuel and oxidizer can reach each other. Recent research has employed nanomaterials to reduce the distance between reactants to increase energy release rates. This dissertation attempts to uncover and quantify structure-function relationships in energetic nanomaterials by modifying chemical and physical properties of the materials and characterizing the observed changes using new diagnostic tools. This dissertation begins with the development of diagnostic tools that can capture the dynamics of energetic material combustion using a high-speed color camera to measure temperature. This tool has also been modified into a high-speed microscope that allows for spatial and temperature measurements at microscale length (µm) and time (µs) scales. Changes to chemical formula have been explored for energetic nanomaterial systems, though visualization of the reaction dynamics limited detailed results on reaction mechanisms. The first study performed here probed the role of gas generation vs. thermal effects in energy release rate where it was found that combustion inefficiencies from reactive sintering could be mitigated by introducing a gas-generating oxidizer. To explore combustion improvements in the fuel, a metal fuel nanoparticle manufacturing method was explored, though the combustion performance was again limited by reactive sintering. Another effort to reduce reactive sintering with a gas generator proved successful, but also unveiled the importance of different heat transfer mechanisms for propagation. The role of physical architecture on propellant combustion was also investigated to improve efficiency and versatility in solid propellants. It was found that addition of a poor thermal conductor to a propellant mixture increased the propagation rate of the material and this was attributed to the result increase in burning surface area resulting from inhomogeneous heat transfer. Lastly, this dissertation explores a method to remotely ignite materials using microwaves and titanium nanoparticles. This work sets the stage for a remotely staged solid propellant architecture that would provide control over solid propellant combustion in-operando.Item CO-CULTURE OF BONE MARROW STROMAL CELLS AND CHONDROCYTES FOR BONE TISSUE ENGINEERING: MICROARRAY STUDY OF CHONDROCYTE SECRETED FACTORS(2011) Janardhanan, Sathyanarayana; Fisher, John P; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Tissue engineering refers to the assembly of biomaterials, cells and signaling molecules to develop functional tissues based on strategies derived from developmental processes. Cells play a crucial role, in that they can secrete a library of molecules, not entirely characterized in the laboratory, and yet provide repeatable results during in vitro experiments. Under conditions of co-culture with mesenchymal stem cells, the underlying biology of chondrocytes can elucidate the signal expression during the early bone development process called endochondral ossification. This interaction is tightly regulated in chondrocytes and results in the recruitment and differentiation of mesenchymal stem cells (MSCs) into osteoblasts. We executed a co-culture system, to observe the potential of alginate encapsulated bovine articular cartilage chondrocytes to induce osteogenic differentiation of bovine bone marrow stromal cells and to observe the interaction on a global scale by making use of the microarray platform. We identified certain genes expressed by chondrocytes that show substantial activity in co-culture systems such as versican (VCAN), secreted frizzled related protein 1 (SFRP1), matrix metallopeptidase 13 (MMP13), extracellular matrix protein 1 ( ECM1) and collagen type 1 ( Col1A1, Col1A2).Item CFD SIMULATIONS FOR SCALE UP OF WET MILLING IN HIGH SHEAR MIXERS(2011) Yang, Meng; Calabrese, Richard V; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Rotor-stator mixers are widely used in the chemical and pharmaceutical process industries. Up to now, however, few papers discuss the mean flow and turbulence fields generated by them and their influence on final product quality. In this work, CFD results at different scales are used to aid in the scale up of crystal wet milling processes. CFD simulations were performed to simulate different scale mixers. In addition, wet milling studies were conducted at the bench scale to complement the CFD results and predict wet milling performance in larger scale mixers. The flow properties in a batch Silverson L4R rotor-stator mixer at 4000 and 6000 rpm were investigated. A hybrid technique was developed. The new method is computationally efficient compared with the standard sliding mesh method. Macro scale properties are predicted. The turbulent flow field and deformation rate field are compared and analyzed. After obtaining fully converged flow fields, one way coupled particle tracking calculations were performed using an efficient fast particle tracking code. Particles trajectories were recorded, and analyzed. To validate the simulated flow field, particle image velocimetry (PIV) experiments were conducted. CFD simulations of Silverson inline L4R (bench scale), 450LS (pilot scale) and 600LS (plant scale) mixers were conducted at constant tip speed to investigate the scale up effect. The macro scale properties werer predicted. The mean velocity, turbulent and deformation rate fields were investigated. The flow properties of the 450LS and 600LS mixers are quite similar, but they are significantly different from those of the L4R (bench scale) mixer. Therefore, it may be resonable to scale up from pilot scale to plant scale by the general accepted tip speed scale up criterion. However, considering tip speed alone may lead to a significant discrepancy between bench scale and larger scales. Bench scale wet milling experiment were performed at 4000, 6000 and 8000 rpm using sucrose and mannitol in the Silverson L4R inline mixer. The crystal size decreases with rotation rate at both free pumping conditions and constant flow rate conditions. To investigate the effect of flow rate, wet milling of granulated sucrose in the Silverson L4R inline mixer with constant rotor tip speed were performed at different flow rates. It is found that the crystal size increases with the flow rate.Item Harnessing the Potential of the Escherichia coli RpoS Phenotype via an Inducible Small RNA Regulatory Platform(2011) Carter, Karen; Bentley, William E; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Recent recognition of the pervasiveness of non-coding RNAs, in both prokaryotic and eukaryotic systems, has prompted metabolic engineers to reevaluate the role of RNAs in a traditionally protein dominated realm. More specifically, bacterial trans-encoded sRNAs have been implicated in the regulation of genes in several critical pathways from quorum sensing to stress responses. The task of responding to stressful conditions, as well as stationary phase, in a comprehensive manner falls to the Escherichia coli global stress regulator, RpoS. Genes transcribed by RpoS are involved in motility, biofilm formation and nutrient limitations. One of the challenges modulating RpoS control is its polymorphic nature. We think this can be addressed using an inducible sRNA regulatory platform. Recent studies have confirmed RpoS to be post-transcriptionally regulated by at least four sRNAs: three activators, DsrA, RprA and ArcZ, and one repressor OxyS. Each of these senses different stress conditions, allowing RpoS synthesis to increase or decrease in response to various stressors. This work investigates the potential of a genetically engineered interchangeable small RNA based gene regulation platform as a switch to affect the expression profiles and metabolic behavior of RpoS. RprA and OxyS were put under the control of an arabinose inducible promoter to test the ability to increase/decrease RpoS protein levels and subsequent changes in RpoS-dependent genes. We then assessed gene expression and phenotypic changes using RT-PCR, Western blotting, microarray and motility and biofilm assays. Positive modulation of RpoS using the pRprA platform resulted in a 2-fold decrease in motility in Top10 cells. This difference in motility improved biofilm formation levels up to 12-fold when compared to direct overexpression of RpoS protein. The positive effect of biofilm formation was further supported by the upregulation of other genes essential for biofilms. Conversely, negative modulation of RpoS using the pOxyS platform resulted in an increase in the transcription of the motility gene, flhD. Both systems were capable of positively and negatively regulating bacterial RpoS protective genes. The ability to deliberately and purposefully control RpoS protective genes, in conjunction with motility and biofilm formation, can potentially have broad impact on biotechnology applications.Item Desing of Click Hydrogels for Cell Encapsulation(2011) Breger, Joyce; Wang, Nam Sun; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The long-term stability of ionically crosslinked alginate hinders the development of a bioartificial pancreas for the treatment of Type I Diabetes. Ionically crosslinked alginate with divalent cations is traditionally utilized to encapsulate islets of Langerhans serving as a protective barrier between the host's immune system and the donor islets of Langerhans. However, due to ion exchange with monovalent ions from the surrounding serum, alginate degrades exposing donor tissue to the host's immune system. The overall goal of this dissertation was to explore the possibility of utilizing `click' chemistry to introduce covalent crosslinking in alginate for therapeutic cell encapsulation. `Click' chemistry is customarily defined as the Cu (I) catalyzed reaction between an azide and alkyne to form a 1,2,3 triazole ring. To achieve the goal of covalently crosslinked polysaccharides, the following aims were determined: (1) synthesis and characterization of functionalized polysaccharides (alginate and/or hyaluronic acid) with alkyne or azide end groups; (2) measurement and comparison of the stability and transport properties of covalently crosslinked alginate hydrogels to that of ionically crosslinked alginate hydrogels; (3) determination of the inflammatory potential and cytotoxicity of these functionalized polysaccharides and `click' reagents by employing RAW264.7, a murine macrophage cell line under various simulated inflammatory states (with or without endotoxin, with or with out the inflammatory cytokine gamma-interferon); (4) optimization of the `click' reaction for therapeutic cell encapsulation utilizing RIN-5F, a rat insulinoma cell line, while minimizing cytotoxicity and maintaining insulin production; (5) encapsulation of primary porcine islets of Langerhans in either ionically and/or covalently crosslinked alginate capsulation and comparing insulin response to a glucose challenge. The results of these experiments demonstrate the utility of employing `click' chemistry to increase the overall stability of alginate hydrogels while maintaining therapeutic cell function.Item New Classes of Self-Assembled Structures in Nonpolar Solvents(2011) Lee, Hee-Young; Raghavan, Srinivasa; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Many researchers have investigated the self-assembly of amphiphilic molecules in water into characteristic structures such as micelles and vesicles. In comparison, amphiphilic self-assembly in nonpolar organic liquids, which can be referred to as "reverse" self-assembly, is much less studied. In this dissertation, we describe a variety of new reverse self-assembled structures formed from amphiphilic molecules. Especially, we focus on long reverse cylindrical structures that can induce high viscosity, and reverse vesicles, i.e., hollow spherical containers surrounded by reverse bilayers. We expect that these reverse structures may be useful for applications such as gelling agents for fuels and oils, hosts for enzymatic reactions, and controlled release. In the first part of this study, we describe the effects of adding inorganic salts to solutions of lecithin in nonpolar solvents. Lecithin is a zwitterionic, mono-unsaturated phospholipid that by itself forms reverse spherical micelles. Salts can be dissolved in these solvents in the presence of lecithin. Interestingly, salts of multivalent cations like calcium (Ca2+), magnesium (Mg2+), lanthanum (La3+) and cerium (Ce3+) greatly increase the viscosity of lecithin sols and transform them into optically transparent organogels. In comparison, monovalent cations or transition-metal cations have negligible effect on reverse self assembly. Based on data from small-angle neutron scattering (SANS), we show that gelation is accompanied by a transition from spherical micelles to cylindrical micelles/filaments. The varying abilities of different cations to induce gelation is shown to correlate with their binding tendencies to the phosphocholine headgroups of lecithin. Next, we describe a class of photorheological (PR) fluids based on a nonpolar solvent such as cyclohexane. The rheological properties of these fluids can be reversibly tuned by UV and visible light. In order to create such PR fluids, reverse wormlike micelles of lecithin + sodium deoxycholate (SDC) are doped with a photoresponsive compound, spiropyran (SP). Spiropyrans can be reversibly converted from a closed-form (SP) to an open-form (MC) by UV and visible light, respectively. Initially, the reverse micelles in the lecithin/SDC/SP system are long and entangled, which makes the solution highly viscous. When exposed to UV light, the viscosity of these micellar solutions drops by a factor of 10. Conversely, when exposed to visible light, the viscosity recovers to approximately its initial value. We have found that this cycle between high and low viscosity states can be repeated more than 10 times. Finally, we describe a new route to forming bilayered structures such as reverse vesicles and lamellae in organic solvents such as cyclohexane. This involves the combination of a saturated phospholipid, dimyristoyl phosphatidyl choline (DMPC) with an inorganic salt having either a trivalent cation like gadolinium (Gd3+) or a divalent cation like calcium (Ca2+). We find that the addition of the salt to DMPC solutions leads to either cylindrical aggregates or bilayered aggregates depending on the concentration of the salt. The structural changes can be explained qualitatively in terms of changes in the molecular geometry (packing parameter) induced by the binding of cations to the headgroups of the phospholipid.Item NEW ELECTROLYTE AND ELECTRODE MATERIALS FOR USE IN LITHIUM- ION BATTERIES(2010) Basrur, Veidhes; Raghavan, Srinivasa; Wang, Chunsheng; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Lithium-ion batteries have emerged as the preferred type of rechargeable batteries, but there is a need to improve the performance of the electrolytes and electrodes therein. Here, we report studies on new electrolyte and anode materials for use in such batteries. First, we report a class of gel electrolytes prepared by utilizing the synergistic interactions between a molecular gelator, 1,3:2,4-di-O-methylbenzylidene-D-sorbitol (MDBS), and a nanoscale particulate material, fumed silica (FS). When MDBS and FS are combined in a liquid electrolyte of propylene carbonate and lithium perchlorate, the liquid is converted into a free-standing gel due to the formation of a strong MDBS-FS network. The gel exhibits an elastic shear modulus ~ 1000 kPa and a yield stress around 15 kPa - both values far exceed those obtainable by MDBS or FS alone in the same liquid. The electrolyte also shows high conductivity (~ 5 x 10-3 S/cm), a wide electrochemical stability window (up to 4.5 V), and good interfacial stability with lithium electrode. In the second study, we describe a new polymeric binder [(poly(acrylamide-co-acrylic acid)] for use in conjunction with silicon (Si) anodes. This binder was combined with Si particles to form composite anode materials, which were then subjected to galvanostatic charge-discharge tests. Capacities exceeding 1000 mAh/g after 120 cycles have been obtained depending on the molecular weight of the binder and the concentration of the Si particles. The above binder thus presents a viable alternative to carboxymethyl cellulose (CMC), which is the current benchmark binder material for Si anodes.Item COMPUTATIONAL STUDIES ON THE BINDING AND DYNAMICS OF THE OSH4 PROTEIN OF YEAST AND A MODEL YEAST MEMBRANE SYSTEM(2010) Rogaski, Brent Joseph; Klauda, Jeffery B; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Osh4 is an oxysterol binding protein homologue found in yeast that is essential for the intracellular transport of sterols. It has been proposed that Osh4 acts as a lipid transport protein, binding a single sterol residue and transporting it from the endoplasmic reticulum to the plasma membrane. The dynamics of Osh4 as well as ergosterol binding was observed using molecular dynamics simulations. Blind docking of several model lipid head group moieties was used to detect potential binding regions along the Osh4 surface favorable towards phospholipid interaction. Models frequently docked to a lysine-rich region on the side of the protein's β-barrel. A model ergosterol-containing membrane system for yeast was also constructed and simulated using molecular dynamics, and an improvement to the deuterium order parameters was observed over previous models. Understanding how Osh4 attaches to cellular membranes will lead to a clear understanding of how this protein transports sterols in vivo.Item Motion of elastic capsules in microfluidic channels(2010) Kuriakose, Shugi; Dimitrakopoulos, Panagiotis; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Capsule flow dynamics in microchannels plays a significant role in complex biological phenomena, such as the microcirculation, and in engineering applications, such as in microfluidic devices for drug delivery and cell sorting. In this thesis, we investigate the motion of elastic capsules in wall-bounded flows by extending the Membrane Spectral Boundary Element method developed by Dodson and Dimitrakopoulos for free-suspended flows. First, a validation study of the method is performed for the axisymmetric capsule motion in a cylindrical channel. For a capsule moving along the centerline of a cylindrical channel, our computational model successfully reproduced the parachute shape observed in earlier experimental and computational studies. Next, we investigate the flow dynamics of a strain-hardening Skalak capsule moving along the centerline in a square and a rectangular channel. We examine how the capillary number and capsule size influence the deformation and physical properties of the capsule. For large capsules in a square channel, our investigation reveals that the steady-state capsule shape is non-axisymmetric. The capsule assumes a shape similar to the channel's cross-section i.e. a square shape with rounded edges. Buckling of the capsule's upstream end resulting in a negative edge curvature is observed at higher capillary numbers and for large capsule sizes. For the largest capsules studied, we also observe the development of dimples at the capsule's lateral surface. A comparative study of capsule motion and deformation in cylindrical and square channels shows that the capsule deformation in a cylindrical channel is similar to that in a square channel at a larger capillary number. In a rectangular channel, we observe a three-dimensional (i.e. non-axisymmetric) deformation of the capsule at high capillary numbers resulting in dimpling of the capsule's upstream end at steady state. We also consider the transient motion of a capsule in a converging square microchannel and investigate the influence of viscosity ratio, capillary number and capsule size on the evolution of capsule properties. As the capsule moves through the converging region a fluctuation in the geometric and physical properties of the capsule is observed.Item Proteomic Analysis of Human Urinary Exosomes(2009) Gonzales, Patricia Amalia; Wang, Nam Sun; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Exosomes originate as the internal vesicles of multivesicular bodies (MVBs) in cells. These small vesicles (40-100 nm) have been shown to be secreted by most cell types throughout the body. In the kidney, urinary exosomes are released to the urine by fusion of the outer membrane of the MVBs with the apical plasma membrane of renal tubular epithelia. Exosomes contain apical membrane and cytosolic proteins and can be isolated using differential centrifugation. The analysis of urinary exosomes provides a non-invasive means of acquiring information about the physiological or pathophysiological state of renal cells. The overall objective of this research was to develop methods and knowledge infrastructure for urinary proteomics. We proposed to conduct a proteomic analysis of human urinary exosomes. The first objective was to profile the proteome of human urinary exosomes using liquid chromatography-tandem spectrometry (LC-MS/MS) and specialized software for identification of peptide sequences from fragmentation spectra. We unambiguously identified 1132 proteins. In addition, the phosphoproteome of human urinary exosomes was profiled using the neutral loss scanning acquisition mode of LC-MS/MS. The phosphoproteomic profiling identified 19 phosphorylation sites corresponding to 14 phosphoproteins. The second objective was to analyze urinary exosomes samples isolated from patients with genetic mutations. Polyclonal antibodies were generated to recognize epitopes on the gene products of these genetic mutations, NKCC2 and MRP4. The potential usefulness of urinary exosome analysis was demonstrated using the well-defined renal tubulopathy, Bartter syndrome type I and using the single nucleotide polymorphism in the ABCC4 gene. The third objective was to study the normal variability between proteomes of female and male urinary exosomes, and to implement a normalization method to analyze urinary exosome samples. Only 19 proteins had a 2-fold change representing 4.9% of the total number of proteins identified which shows that there is high concordance between proteomes of urinary exosomes isolated from males and females. The normalization method, timed urine collection did not correlate as expected with the intensity signal of MVB markers, TSG101 and Alix. This research shows that the proteomic analysis of human urinary exosomes can be the basis for future biomarker studies as well as physiological studies.