Affordable technologies for point-of-care diagnostics
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Affordable, point-of-care diagnostics are needed for disease monitoring in low- resource settings (LRS). Gold-standard laboratory tests require expensive benchtop equipment, which limits their widespread use. In this work, I developed low-cost technologies for the transduction of two independent types of biosensors. In the first part of my work, I developed inexpensive gold leaf electrodes that can be used to build electrochemical biosensors; I use these electrodes to detect clinically relevant viral loads human papillomavirus (HPV) from clinical samples. In the next part of my work, I built an optical setup using off-the-shelf parts for the inexpensive detection of a fluorescent progesterone biosensor; next, I translated this solution-based progesterone biosensor into a paperfluidic format for inexpensive point-of-care testing. The first technology I developed were gold leaf electrodes as a cheaper alternative to conventional gold electrodes. Gold electrodes are commonly used as substrates for biosensors due to the ease of surface modification through the self- assembly of thiolated molecules. However, conventional gold electrodes are often costly and laborious to fabricate, rendering them inappropriate for many applications in low- resource settings. Here, I developed the first integrated, three-electrode biosensor fabricated using pure gold leaf, an inexpensive and widely available material; each device uses only $0.16 worth of gold. Importantly, my fabrication scheme does not require any specialized equipment or clean room space, enabling my fabrication process to be carried out anywhere it is needed. As a proof of concept of this platform, electrodes were modified with DNA for CRISPR-based detection of clinically relevant viral loads (1.2 x 104 total copies) of HPV 18 DNA that had been extracted from clinical samples. Next, I developed a benchtop optical device using inexpensive-off-the shelf parts for fluorescent detection of a transcription-factor based biosensor. This transcription- factor based biosensor detected progesterone as a model target. This optical device worked as well as a multi-thousand dollar plate reader. Next, I adapted the solution- based progesterone biosensor to a paper-based biosensor for the affordable and portable progesterone monitoring. This device had a lower limit of detection of 27 nM, which is a clinically relevant level of progesterone in both cows and premenopausal women.