Investigation of reagent storage and electrochemical testing on filter paper
Diagnosis and detection is one of the most effective means of controlling matters that adversely affect public health and safety. Yet, in the developing world with a high burden of disease, most gold standard diagnostics remain widely inaccessible due to cost and lack of infrastructure. In recent years, one strategy to increase access to health and safety devices has been through the development of point-of-care diagnostics that are low-cost, portable, and easy-to-use for on-site analysis. In particular, paper has recently been in the spotlight as such a point-of-care (POC) platform. Compared to conventional POC tests made of glass or plastic substrates, paper itself is even thinner, light-weight, portable, disposable, and can store biological and chemical molecules for analytical measurement within its fibrous network. Several paper-based tests have demonstrated high sensitivity and specificity to detect proteins, bacteria, and metals for applications in disease diagnosis, health monitoring, and food and water safety. However, several gaps still remain in order to fully develop these paper-based analytical devices for point-of-care use in low-resource settings. First, reagent stability on filter paper is poorly understood, as well as its influence on quantitative, long-term testing. Second, the need for specialized instrumentation to perform the analytical methods on the paper devices can be a logistical and financial burden to end users in resource-limited settings. This dissertation addressed these questions through the development of quantitative paper assays for robust and point-of-care testing in low-resource settings. First, we fabricated micro-paper electrochemical devices, or µPEDs, for the amperometric detection of ethanol. This target analyte has direct applications in the global issue of road safety, which claims thousands of lives due to driving under the influence of alcohol. Also, we demonstrate that ethanol detection can provide the basis for the novel detection of substandard misoprostol, a high impact drug to save mothers from post-partum bleeding that is often the reason for maternal mortality. Second, we developed an independent method to study reagent stability on filter paper under conditions likely encountered in low-resource settings. Methods that enhanced stability were also used in the development of the µPEDs. Finally, we demonstrate that the ethanol measurements on our µPEDs could be performed with a commercial glucose meter, which operate by the same principles required to measure analyte concentrations. This integration of device and reader presents a cheap, reliable, low-power, and portable platform that can be adapted for the detection of other analytes relevant to health and safety.
Thesis (Ph.D.)--Boston University