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School of Chemical and Biomolecular Engineering Seminar Series

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Now showing 1 - 10 of 25
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    Molecular Engineering of Stem Cell and Gene Therapies
    (Georgia Institute of Technology, 2009-12-02) Schaffer, David V.
    There are numerous diseases for which there is still no cure, and new molecular therapies based on stem cells and gene delivery have significant therapeutic potential. Before these approaches can succeed, however, a number of fundamental challenges must be overcome, particularly in the nervous system, our tissue of interest. Stem cells have significant potential for treating a wide variety of disorders, and their successful integration into such therapies will hinge upon three critical steps: their expansion without differentiation (i.e., self-renewal), their differentiation into specific cell types, and their functional integration into existing tissue. Precisely controlling each of these steps will be essential to maximize their therapeutic efficacy, as well as minimize potential side effects. We combine experimental and computational approaches to understand basic mechanisms by which microenvironmental signals regulate of stem cell fate choice, including neural stem and human embryonic stem cells. Furthermore, we have applied this basic information towards the engineering of synthetic, biomaterial based microenvironments for the expansion and differentiation of stem cells. Gene therapy, introduction of genetic material to the cells of a patient for therapeutic benefit, has enormous potential to synergize with stem cells to repair damaged tissue through the delivery of genes to control stem cell function. However, the vehicles or vectors that deliver therapeutic nucleic acids require highly challenging engineering for enhanced efficiency and safety. Our efforts are focused on engineering vehicles based on viruses at the molecular level to overcome the common dilemma faced by all: they did not evolve in nature to perform the therapeutic endeavors we ask of them. Specifically, we are applying directed evolution approaches to fundamentally change the properties of viruses at the molecular level. We hope that these capabilities can be combined to regenerate tissue from the effects of devastating, chronic disorders, such as Alzheimer’s, Parkinson’s, and Lou Gehrig’s Diseases.
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    Computer-Aided Molecular Design: Approaches and Applications
    (Georgia Institute of Technology, 2009-11-04) Visco, Donald P., Jr.
    Computer-aided molecular design (CAMD) is a cost-effective technique which allows researchers to computationally generate molecular structures according to an algorithm and score those structures for fitness. While CAMD has had notable achievements in the drug design area, it is also used in the chemical process industry. In this presentation, I will provide background on some of the basic CAMD techniques and successes. Additionally, I will focus on one such technique using the Signature molecular descriptor. We will show that Signature possesses desirable features (relative to other descriptors) which make it well-suited for a CAMD approach. Applications to the design of ICAM-1 inhibitors will be presented as well as other studies using this approach, including solvent design and ionic liquids as biomass pretreatment options.
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    Cell and Particle Behavior in Microfluidic Mixers: Applications in Cell Signaling Dynamics
    (Georgia Institute of Technology, 2009-10-14) Hirsch, Alison
    Fluid mixing is common in large-scale chemical processes. Recently, many biological or chemical processes are carried out in microfluidic systems, where mixing of solutes is predominantly a diffusion process due to the laminar nature of the flow at the micro scale. Different mixing strategies have been employed to effectively decrease the characteristic length for diffusion. However, particle mixing behavior in fluid is still not well understood. To assess the critical factors behind fluid-particle behavior at Reynolds numbers where inertial and viscous forces both play a role, we experimentally studied three dimensional particle distributions as a function of flow velocity, fluid and particle properties, and mixer geometries, using a fast microscopy technique we developed. Computational Fluid Dynamics was also used to understand the particle flow characteristics as influenced by relevant forces. With this knowledge, efficient unit operations in multiphase systems (e.g. mixing and separation) can be designed, especially in microfluidic technologies for many biological and medical applications that handle cells and beads. In particular, for our study in the signaling dynamics in T cell activation for adoptive-transfer cancer immune therapy. The microchip in this case provides a platform for obtaining well-controlled data points in parallel, superior to bench-top assay performances.
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    Three-dimensional in Situ Temperature Measurement in Microsystems Using Brownian Motion of Nanoparticles
    (Georgia Institute of Technology, 2009-10-14) Chung, Kwanghun
    Recent developments in microsystems for chemical and biological analysis offer significant advantages over conventional methods, such as precise manipulation of samples and control of microenvironment. For many applications, the ability to control and measure temperature inside microfluidic devices is critical since temperature often affects biological or chemical processes. To address this need, we developed an in situ method for three-dimensionally resolved temperature measurement in microsystems. The temperature of the surrounding fluid is correlated from Brownian diffusion of suspended nanoparticles. We use video-microscopy in combination with image analysis software to selectively track nanoparticles in the focal plane. This method is superior with regards to reproducibility and reduced systematic errors since measuring Brownian diffusivity does not rely on fluorescence intensity or lifetime of fluorophores. The efficacy of the method is demonstrated by measuring spatial temperature profiles in various microfluidic devices that generate temperature gradients and by comparing these results with numerical simulations. We show that the method is accurate and can be used to extract spatial temperature variations in three dimensions. Compared to conventional methods that require expensive multiphoton optical sectioning setups, this technique is simple and inexpensive. In addition, we demonstrate the capability of this method as an in situ tool for simultaneously observing live cells under the microscope and monitoring the local temperature of the cell medium without biochemical interference, which is crucial for quantitative studies of cells in microfluidic devices.
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    Volume-Phase Transitions in Surface-Tethered Networks and Implications for Swelling Instabilities
    (Georgia Institute of Technology, 2009-09-16) Toomey, Ryan
    The overall thrust of our research program is to develop responsive structures without the need for complex circuitry or bulky instrumentation. Our approach is to use polymers that undergo volume-shape changes in response to an external stimulus. The stimulus alters the balance of hydration forces within the polymer network, resulting in changes to the macroscopic properties. In this talk, I will discuss the role of intermolecular forces and how they can be harnessed to control volume-phase transitions in polymer networks. I will also discuss techniques for fabricating surface-confined networks, including soft lithography and photo-lithography strategies, as well as the effect of surface-confinement on the response characteristics of the polymers. Finally, it will be shown how instabilities can be induced in hydrogel microstructures to facilitate reconfigurable topographies with sensing and actuation integrated at the material level. Such reconfigurable surfaces can have important implications for variable adhesion, self-cleaning materials, and separations.
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    Functionalized Nanostructured Tri-Block Copolymer Ionomers for Separations and Fuel Cell Applications
    (Georgia Institute of Technology, 2009-09-09) Rosado, David Suleiman
    Proton exchange membranes (PEMs), commonly used in direct methanol fuel cells (DMFC), are typically limited by either high methanol permeability (also known as the cross-over limitation) or low proton conductivity. A potential alternative to this problem is to use thermoplastic elastomers (TPE) with rubbery and glassy thermodynamically immiscible microphases. The glassy segment is often composed of polystyrene, which can be sulfonated to high ion exchange capacities (IEC), and thus creates ion containing polymers or ionomers. Linear poly-styreneisobutylene- styrene (SIBS) and both, linear and branched poly-styrene-isoprene-styrene (SIS), were sulfonated and functionalized with different cations (size and electronegativity). Controlling the degree of sulfonation and the functionalization allowed for selective membranes that could be used for applications such as fuel cells, gas sensors, and permselective separations. In addition, supercritical fluid processing allowed for additional morphological changes, especially with perfluorinated membranes. This presentation will review some of the critical materials characterization results including elemental analysis (EA), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and Fourier transform infrared spectroscopy (FT-IR). The kinetic and transport properties will also be discussed for the development of separation processes and catalytic nanochannel reactor arrays for fuel cell applications.
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    Control of Microfluidic Devices
    (Georgia Institute of Technology, 2009-04-22) Burns, Mark A.
    The field of microfluidics is uniquely poised to significantly impact the biomedical sciences through the miniaturization and massive parallelization of biochemical assays. For example, future advances in microfluidics could revolutionize disease diagnosis, drug discovery, and pathogen detection. In our work, we focus on components and integrated systems that can be used in health-related biochemical analysis. Construction of such systems is currently relatively easy; there are a large number of published “lab on a chip” systems constructed from a variety of substrates using different actuation, sensing, and control components. However, there are still relatively few microfluidic diagnostic systems commercially available. Although there are many reasons, one possible explanation for this scarcity is the complex interconnect requirements of many pneumatically actuated analysis chips. In an attempt to overcome this disadvantage, we have developed microfluidic components and systems that strive to reduce the required number of pneumatic interconnects. For instance, a single pressure input can be sent to multiple temperature-regulated venturis, each of which is capable of generating a unique pressure signal. In addition to electronically controlled components, pneumatically controlled components can be used such as pneumatic logic gates and decoders. These and other components will be discussed in terms of integrated biochemical analysis systems.
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    Integration of Production Planning and Scheduling in the Chemical Industry
    (Georgia Institute of Technology, 2009-04-15) Maravelias, Christos T.
    To remain competitive in today’s environment, chemical companies must adopt an integrated view across all their operations and use advanced planning methods to achieve enterprise-wide optimality. At the production level, it is necessary to simultaneously consider medium-term (planning) and short-term (scheduling) decisions. Despite recent advances in computer hardware and optimization software, current methods are insufficient to address real-world instances of this integrated problem. Three approaches to this integrated problem are discussed. First, a novel formulation for the “generalized” lot-sizing problem is presented. This formulation accounts for process characteristics that are common in the chemical industry but are not addressed by existing approaches. Second, a number of theoretical results for discrete-time formulations are developed, enabling us to formulate problems that can be solved very effectively. Third, we present how detailed scheduling models can be used off-line to obtain an approximation of feasible production levels and an underestimation of production cost. Finally, we present how these methods can be used to address large-scale integrated planning-scheduling problems.
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    Proteins That Nature Never Made
    (Georgia Institute of Technology, 2009-04-01) Tirrell, David A.
    Macromolecular chemistry has traditionally been divided into two fields, with biochemists and biochemical engineers working on proteins and nucleic acids while polymer chemists and materials scientists have concerned themselves with synthetic polymers. These two classes of macromolecules have profound differences: proteins and nucleic acids are uniform, well-folded, and evolvable, whereas polymers are heterogeneous and tend to adopt random-coil conformations. These differences in molecular structure and behavior have led to striking differences in how natural and synthetic polymers are used - largely for information storage and transfer in biology, and largely as materials in the technological world. This lecture will describe an ongoing attempt to bridge the gap between polymers and proteins by using artificial genes to direct the synthesis of artificial proteins in bacterial cells and to combine the physical and informational properties of macromolecules.
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    Fog Chemistry and Air Pollution in the U.S. Gulf Coast Region
    (Georgia Institute of Technology, 2009-03-11) Valsaraj, Kalliat T.
    Aerosols in the atmosphere play a critical role in determining the fate of atmospheric pollutants and also influence global climate change. Fog is a lower atmospheric, near-surface cloud and plays a role in determining local weather patterns. In this respect fog-processing of organic chemicals is important to understand. Relatively little is known about the organic composition of fog in many parts of the world and approximately 50% of material in fog has not been characterized. Atmospheric transformations in a foggy environment are driven by heterogeneous reactions in thin water films (< 10μm), which have been largely unexplored. Our laboratory has been engaged in a six year field and laboratory project understanding the chemistry of fog in the Gulf Coast region between Houston and Baton Rouge. This seminar will summarize our recent work in this field.