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Doctor of Philosophy (PhD)
Year Degree Awarded
Month Degree Awarded
Sam R. Nugen
D. Julian McClements
Sarah L. Perry
Paper based devices are an emerging trend for micro total analysis systems due to their rapid, sensitive and specific attributes. Lateral flow assays (LFAs), the predecessor of paper-fluidic devices, are developed for many applications which range from nucleic acid and antibody detection to commercial home pregnancy tests. With growing interest in replacing conventional detection methods, multistep assays are needed. These assays require multiple test reagents, therefore, there is a need to control fluid flow for the development of complex paper-based devices.
We were able fabricate paper-fluidic platforms where we used electrowetting-on-dielectrics to create valves on paper. With this method, we directly controlled the timing and flow of the fluid. However, the electrowetting valves required an external power source for actuation, thus we developed a passive fluid control method.
To do this, passive delay valves/barriers were inkjet-printed, by altering the drop spacing of the ink creating effective delay barriers, which decreases the rate of capillary action of the throughput solution. The patterned devices were later used to create a paper based device where an amplified nucleic acid assay was performed.
After creating a paper based platform and understanding the properties that control fluid flow on paper, it is important to discover applications that are suitable for the devices. Phage amplified LFAs were developed, where a genetically engineered phage that overexpresses alkaline phosphatase was used, in combination with phage amplification kinetics to detect for low levels of E. coli in a sample. In the end, we were able to fabricate a barcode style LFA that had a visually quantitative colorimetric readout.
After understanding phage kinetics and amplification, their infectious and destructive mechanism was leveraged and applied to decontamination of agricultural rinse water. In general, bacteriophages are capable of infecting and lysing target bacteria and are kept viable by lyophilization, but freeze-drying is time consuming and requires large machinery. In our study, we dehydrated bacteriophages in electrospun nanofibers and studied the effects of excipients in polymeric solutions and different storage conditions on bacteriophage viability. Ultimately, electrospun nanofibers stored for eight weeks at ambient temperatures retained high phage viability which is sufficient for infection.
Koo, Charmaine K.W., "Advanced Materials for Rapid Diagnostics in Food, Agriculture and Healthcare" (2016). Doctoral Dissertations. 651.