Development of Fluorescence-based Optical Detection Techniques for Accessible and Efficient Point-of-Care Diagnostics
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Diagnostics performed at the point of care need to provide portable, rapid, inexpensive, and accurate results while overcoming challenges not typically seen in a central laboratory setting. Fluorescence microscopy gives a unique opportunity to address these needs. Since fluorescence looks for the presence of a target rather than morphological features in a sample, optical performance requirements may be reduced and medical device designs may be simplified. In this dissertation, the development of two classes of devices are presented. The first application targets white blood cell (WBC) differential counting, which can be used to determine bacterial or viral infections, evaluate allergic conditions, diagnose and monitor malignant diseases such as leukemia, and stage HIV infections. Two devices were developed to perform WBC differential counting: (1) a tunable fluorescence microscope using electrowetted lenses and (2) a fluorescence microscope using an ultraviolet (UV) LED as an excitation source. The electrowetted lenses incorporated in the tunable microscope were used to sharply focus on a specific wavelength at a time, simplifying the optical design as chromatic aberrations did not need to be corrected. The use of UV in the second system allowed for the removal of excitation, emission, and dichroic filters, as UV is absorbed by glass components, detectors are typically not sensitive to UV, and many fluorescent dyes are excitable by UV. Thus, this microscope could be fabricated out of commercial optics and use commercially available, low cost sample cartridges. The second application in the dissertation targets patient monitoring for tuberculosis (TB) treatment. Mycobacteria have an intrinsic molecule (thought to be used during metabolism) that is autofluorescent. This molecule had been previously shown in methanobacteria to have different photobleaching rates based on whether the molecule resided in live or dead organisms. Tracking of changes in autofluorescence decay may be used to augment current TB patient monitoring methods that cannot determine viability of organisms and may additionally reduce the time to determining viability from weeks to minutes.
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Wong, Cynthia. "Development of Fluorescence-based Optical Detection Techniques for Accessible and Efficient Point-of-Care Diagnostics." (2019) Diss., Rice University. https://hdl.handle.net/1911/105971.