Browsing by Subject "lab-on-a-chip"
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Item Porous Membrane-Based Sensor Devices for Biomolecules and Bacteria Detection(2012-10-19) Tsou, Pei-HsiangBiological/biochemistry analyses traditionally require bulky instruments and a great amount of volume of biological/chemical agents, and many procedures have to be performed in certain locations such as medical centers or research institutions. These limitations usually include time delay in testing. The delays may be critical for some aspects such as disease prevention or patient treatment. One solution to this issue is the realization of point-of-care (POC) testings for patients, a domain in public health, meaning that health cares are provided near the sites of patients using well-designed and portable medical devices. Transportation of samples between local and central institutions can therefore be reduced, facilitating early and fast diagnosis. A closely related topic in engineering, lab-on-a-chip (LOC), has been discussed and practiced in recent years. LOC emphasizes integrating several functions of laboratory processes in a small portable device and performing analysis using only a very small amount of sample volume, to achieve low-cost and rapid analysis. From an engineer's point of view, LOC is the strategy to practice the idea of POC testing. This dissertation aimed at exploring the POC potentials of porous membrane-base LOC devices, which can be used to simplify traditional and standard laboratory procedures. In this study, three LOC prototypes are shown and discussed. First the protein sensor incorporating with silica nanofiber membrane, which has shown 32 times more improvement of sensitivity than a conventional technique and a much shorter detection time; secondly the bacteria filter chip that uses a sandwiched aluminum oxide membrane to stabilize the bacteria and monitor the efficacy of antibiotics, which has reduced the test time from 1 day of the traditional methods to 1 hour; the third is the sensor combining microfluidics and silica nanofiber membrane to realize Surface Enhanced Raman Spectroscopy on bio-molecules, which has enhancement factor 10^9 and detection limit down to nanomolar, but simple manufacturing procedures and reduced fabrication cost. These results show the porous-base membrane LOC devices may have potentials in improving and replacing traditional detection methods and eventually be used in POC applications.Item Supported phospholipid membranes as biometric labs-on-a-chip: analytical devices that mimic cell membrane architectures and provide insight into the mechanism of biopreservation(Texas A&M University, 2007-09-17) Albertorio, FernandoThis dissertation focuses on the applications of solid supported phospholipid membranes as mimics of the cellular membrane using lab-on-a-chip devices in order to study biochemical events such as ligand-receptor binding and the chemical mechanism for the preservation of the biomembrane. Supported lipid bilayers (SLBs) mimic the native membrane by presenting the important property of two-dimensional lateral fluidity of the individual lipid molecules within the membrane. This is the same property that allows for the reorganization of native membrane components and facilitates multivalent ligand-receptor interactions akin to immune response, cell signaling, pathogen attack and other biochemical processes. The study is divided into two main facets. The first deals with developing a novel lipopolymer supported membrane biochip consisting of Poly(ethylene glycol) (PEG)-lipopolymer incorporated membranes. The formation and characterization of the lipopolymer membranes was investigated in terms of the polymer size, concentration and molecular conformation. The lateral diffusion of the PEG-bilayers was similar to the control bilayers. The air-stability conferred to SLBs was determined to be more effective when the PEG polymer was at, or above, the onset of the mushroom-to-brush transition. The system is able to function even after dehydration for 24 hours. Ligandreceptor binding was analyzed as a function of PEG density. The PEG-lipopolymer acts as a size exclusion barrier for protein analytes in which the binding of streptavidin was unaffected whereas the binding of the much larger IgG and IgM were either partially or completely inhibited in the presence of PEG. The second area of this study presents a molecular mechanism for in vivo biopreservation by employing solid supported membranes as a model system. The molecular mechanism of how a variety of organisms are preserved during stresses such as anhydrobiosis or cryogenic conditions was investigated. We investigated the interaction of two disaccharides, trehalose and maltose with the SLBs. Trehalose was found to be the most effective in preserving the membrane, whereas maltose exhibited limited protection. Trehalose lowers the lipid phase transition temperature and spectroscopic evidence shows the intercalation of trehalose within the membrane provides the chemical and morphological stability under a stress environment.