Development of point-of-care diagnostic technologies for global and mental health

Access to diagnostic testing and screening technologies helps to improve patient care by enabling early treatment and monitoring of patient condition. Most of these technologies, however, rely on laboratory infrastructure and are expensive and time-consuming. In many limited-resource settings, these challenges are too great to overcome, preventing patient access to early diagnosis and screening. Point-of-care diagnostic technologies are designed to fill this need, providing low-cost, easy-to-use, and rapid testing. Lateral flow assays (LFAs) represent a simple platform for biomarker-based point-of-care diagnostics with very low cost and a rapid result. Antigen-antibody binding forms the basis of these tests, with labeled antibodies or proteins typically providing an optical signal that can either be seen by eye or analyzed using imaging devices. Microfluidic assays are another form of biomarker analysis that can be designed to incorporate more complex assays with more steps than a traditional LFA. In this work, we describe our efforts to develop novel and improved immunoassays for use at the point of care based on LFA and microfluidic technologies. The first three chapters of this dissertation describe our work on three different applications of lateral flow technology. We will first discuss our improvements to the detection range of an LFA through periodic measurement of the developing signal and kinetic analysis of the result. This work demonstrated our ability to overcome the high-dose hook effect without altering the LFA or the steps required by the user. Next, we present our point-of-care system for determination of folate status in serum. This technology provides a method for measuring folate concentration in serum without the use of complex technology. Our third lateral flow technology is an LFA to measure cortisol concentration in saliva. This LFA was validated in saliva samples from a human study that analyzed participant alertness and cortisol levels. Our final work describes the design of a microfluidic system for improved sensitivity in measurement of cortisol concentration in saliva. This system incorporates sample collection, filtration, treatment, and transfer to the microfluidic assay. An all-in-one device interacts with a disposable cassette to pump saliva into the microfluidic chip and provide a result