Browsing by Subject "Enzyme-linked immunosorbent assay"
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Item Electrospinning of silica nanofibers: characterization and application to biosensing(2009-06-02) Tsou, Pei-HsiangElectrospinning is a technique to achieve nanometer scale fibers. Similar to the conventional spin methods of making fabric, the viscous polymer solution is ejected from a spinneret; stretched and solidified in the air, the solution forms the fibers. The different part of electrospinning among others is that the fibers are driven by the electrostatic force, which induces the repulsion inside the liquid and further reduces the diameter. The resultant product is a non-woven membrane, which is porous; and the pore size is around several nanometers to a micrometer wide. In this work, the relationship between the diameter of electrospun silica fibers, experimental parameters such as concentration and voltage, and between pore size of the fiber membrane and experimental time were studied. Materials used in the process are Polyvinylpyrrolidone (PVP), butanol and spin-on-glass coating solution, which act as polymer carrier, solvent, and silica-precursor, respectively. Polymer/silica precursor composite fibers were ejected from the needle of a plastic syringe when an electrical field, as high as several kV/cm, was applied. Then silica fibers were achieved by baking the composite ones at 773 oK for 12 h. Electrospun silica nanofibers were characterized as a function of polymer solution parameters. The calcined fibers were examined by using a field emission scanning electron microscope. The results showed that the fiber diameters decrease with decreasing proportion of polymer and silica precursor, and increase with a higher electric field. Pore sizes, defined as the grid areas enclosed by fibers on nearby layers, were also examined and showed no time-dependent tendency when the electrospin time was between 1-5 min. Fiber membranes were then used as the platform for protein detection. The results were compared with the control, which used glass slides as the platform. The results make it possible to make a more sensitive biosensing device.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 Quantifying ricin in agricultural soils(Texas Tech University, 2002-12) Boroda, EliTo date there are no reports of extensive scientific investigations on the analysis, determination or content of ricin, RCAeo (Ricinus communis agglutinin - 60 kDa) in agricultural soils. To accurately quantify the amount of ricin available within the soil, a modified ELISA (Enzyme Linked Immunosorption Assay) was developed. The ELISA followed an extraction process using an isotonic saline solution as a ricin carrier. The range of ricin detection was between 0.010 ^g ricin/g soil to 0.300 |jg ricin/g soil as contrasted with the previously employed radial immunodiffusion assays with a sensitivity limited tol.O mg ricin/gram soil. Using the modified ELISA method, the ricin content in the surrounding soil of germinating castor seeds planted 0.5 cm deep in 25 g of soil was detennined in Olton and Amarillo soils. These two soils are common agricultural soils in Lubbock, Texas area. Ricin was detected in both soils washed off the seeds of germination days four, six and eight days after seeding. Ricin was not detected in days two or ten after seeding. In addition, ricin was not found in any of the remaining soil. An investigation quantifying ricin within a field (30 meters by 152 meters) that had supported a crop of castor (Ricinus communis) in a previous growing season with an intermediate crop of cotton (Gossypium hirsutum), ricin was detected. In a separate field study, ricin was also only detected during the last December sampling of the same year crop. Soil in this study was the Amarillo fine sandy loam. Half of a castor field (121 meters by 121 meters) had been pivot irrigated. The other half had been furrow irrigated. Ricin detected was significantly less in the furrow irrigated half when compared to the center pivot irrigation. Ricin was also noted in response to a controlled stress trial only when the stress consisted of a combination of saline irrigation water EC (Electroconductivity) of 10 dS/m and drought. No other stresses, such as heat (35.0 °C to 38 °C), saline irrigation or drought, alone resulted in any detectable ricin within the sampled the soil. This data suggests that a combination of growth conditions combined with a specific set of external stress factors and human cultivation methods may play a determining role in the natural deposition ricin in agricultural soil as well as its long-term retention.