UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
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Item Microfluidic Planar Phospholipids Membrane System Advancing Dynamics Studies of Ion Channels and Membrane Physics(2012) Shao, Chenren; DeVoe, Donald L; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The interrogation of lipid membrane and biological ion channels supported within bilayer phospholipid membranes has greatly expanded our understanding of the roles membrane and ion channels play in a host of biological functions. Several key drawbacks of traditional electrophysiology systems used in these studies have long limited our effort to study the ion channels. Firstly, the large volume buffer in this system typically only allows single or multiple additions of reagents, while complete removal either is impossible or requires tedious effort to ensure the stability of membrane. Thus, it has been highly desirable to be able to rapidly and dynamically modulate the (bio)chemical conditions at the membrane site. Second, it is difficult to change temperature effectively with large thermal mass in macro device. Third, traditional PPM device host vertical membranes, therefore incompatible with confocal microscopy techniques. The miniaturization of bilayer phospholipid membrane has shown potential solution to the drawbacks stated above. A simple microfluidic design is developed to enable effective and robust dynamic perfusion of reagents directly to an on-chip planar phospholipid membrane (PPM). It allows ion channel conductance to be readily monitored under different dynamic reagent conditions, with perfusion rates up to 20 µL/min feasible without compromising the membrane integrity. It is estimated that the lower limit of time constant of kinetics that can be resolved by our system is 1 minute. Using this platform, the time-dependent responses of membrane-bound ceramide ion channels to treatments with La3+ and a Bcl-xL mutant were studied and the results were interpreted with a novel elastic biconcave distortion model. Another engineering challenge this dissertation takes on is the integration of fluorescence studies to micro-PPM system. The resulting novel microfluidic system enables high resolution, high magnification and real-time confocal microscope imaging with precise top and bottom (bio)chemical boundary conditions defined by perfusion, by integrating in situ PPM formation method, perfusion capability and microscopy compatibility. To demonstrate such electro-optical chip, lipid micro domains were imaged and quantitatively studied for their movements and responses to different physical parameters. As an extension to this platform, a double PPM system has been developed with the aim to study interactions between two membranes. Potential application in biophysics and biochemistry using those two platforms were discussed. Another important advantage of microfluidics is its lower thermal mass and compatibility with various microfabrication methods which enables potential integration of local temperature controller and sensor. A prototype thermal PPM chip is also discussed together with some preliminary results and their implication on ceramide channel assembly and disassembly mechanism.Item BILAYER LIPID MEMBRANE (BLM) INTEGRATION INTO MICROFLUIDIC PLATFORMS WITH APPLICATION TOWARD BLM-BASED BIOSENSORS(2007-04-27) Hromada, Jr., Louis Paul; DeVoe, Donald L; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bilayer Lipid Membranes (BLMs) have been widely used as an experimental tool to investigate fundamental cellular membrane physics and ion channel formation and transduction. Traditional BLM experimentation is usually performed in a macro-sized electrophysiology rig, which suffers from several well-known issues. First, BLMs have short lifetimes (typically on the order of tens of minutes to a few hours) and the laborious, irreproducible membrane formation process must be repeatedly applied for long-term testing. Second, stray capacitance inherent to traditional test rigs limits the temporal response leading, for example, to poor resolution in determining fast ion channel translocation events. Lastly, BLM testing is done within a single site format thus limiting throughput and increasing data collection time. To mitigate the above drawbacks, BLM technology and microfluidic platforms can be integrated to advance the state-of-the-art of BLM-based biosensor technology. Realization of BLM-based microfluidic biosensors can offer significant improvement towards sensor response characteristics (e.g. lower noise floor, increased time response). In addition, microfluidic biosensing chips can be fabricated with multiple BLM test sites that allow for parallel testing thus increasing data collection efficiency. Other benefits that microfluidics offer are: small reagent sensing volumes, disposable packaging, mass manufacturability, device portability for field studies, and lower device cost. Novel polymer microfluidic platforms capable of both in-situ and ex-situ BLM formation are described in this work. The platforms have been demonstrated for the controlled delivery of trans-membrane proteins to the BLM sites, and monitoring of translocation events through these ion channels using integrated thin film Ag/AgCl electrodes. The detailed design, fabrication, and characterization of various micro-fabricated BLM platforms is presented in this dissertation.