Text

theses

ETD doctoral

We live in a world with persistent, emerging, and reemerging infectious disease threats. Infections can be caused by pathogenic microbes, including viruses, bacteria, fungi, and parasites. The detection and identification of these pathogens are critical for diagnosis and treatment. Electrical based biosensor is particularly attractive in recent years due to the ease of operation, rapid processing time, non-necessity of labeling, and the potential of miniaturization. Electrical impedance is a straightforward technique that could identify the presence of biomolecules and cells and enable quantification analysis. In this thesis, I developed an electrical impedance based platform to quantify DNA concentration for viral detection and measure the impedance signature of different phenotypes of microbes for classification and pathogen assessment.

For DNA quantification, we introduce the integration of paramagnetic beads with DNA fragments and apply a custom-made microfluidic chip to detect DNA molecules bound to beads by measuring impedance at multiple frequencies. Technical and analytical performance was evaluated using beads containing short oligonucleotides or purified Polymerase Chain Reaction (PCR) products of different lengths and different concentrations.

Multiplex molecular biomarker analysis is of great importance in many biomedical and clinical studies. Electronic barcoding of micro-particles has the potential to enable multiplexing process. Nano-electronic barcoding works by depositing a thin layer of oxide on the top half of a micro-particle. We expanded library of nine barcoded particles by forming oxide layers of different thicknesses and different dielectric materials using atomic layer deposition and assess the ability to accurately classify particle barcodes using multi-frequency impedance cytometry in conjunction with supervised machine learning.

Separating specific cell phenotypes from a heterotypic mixture is a critical step in many research projects. Here we present the use of electrical impedance as an indicator of cell health and for identifying specific microbial phenotypes. We developed a microfluidic platform for measuring electrical impedance at different frequencies using Staphylococcus aureus and green alga Picochlorum SE3. Our results demonstrate the utility of electrical impedance as an indicator of cell phenotype by providing results that are consistent with known changes in cell size and physiology.

ETD_11410

Ph.D.

Includes bibliographical references

doi:10.7282/t3-sej8-yp24

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