| Healthcare in resource-poor settings is limited by a lack of high quality diagnostic tools appropriate for the point of care. Currently available diagnostic tests, such as ELISA or lateral flow assays, fall short in addressing all of the desired characteristics for the developing world. To meet the needs of a point-of-care diagnostic, a flow-through membrane immunoassay, which leveraged the properties of a porous substrate to perform immunoassays in a fraction of the time but with comparable sensitivity as ELISA, was developed. The universal nature of the assay platform was demonstrated for detection of IgM antibodies specific for several infectious diseases.;Although IgM is a good biomarker for an acute infection, challenges in accurately measuring the presence of disease-specific 1gM exist. Interference from disease-specific IgG can cause false negative or false positive test results, and therefore must be removed from samples prior to testing. To this end, a rapid and specific IgG depletion method was developed which utilized protein G immobilized porous beads mixed with the sample within a batch reactor. In order to properly optimize the procedure, a quantitative study of IgG interference in IgM immunoassays was undertaken. From this work, the amount of IgG to deplete from samples to prevent incorrect test results was elucidated. A computational model of IgG depletion with porous beads in a batch reactor was employed to minimize the time and cost while reaching the required IgG depletion threshold.;Similarly, sample preparation methods that are portable, inexpensive, and require minimal user input are virtually non-existent. To address these limitations, a microfluidic device that integrated all the sample preparation steps: plasma extraction, sample dilution, and clean-up of assay interferents, necessary prior to immunoassay testing was designed. A novel mixer, which utilized bubbles generated from a pneumatic source for fluid circulation, was employed for sample dilution and IgG depletion. In addition, methods for dehydrated, on-card reagent storage without refrigeration were validated. The end result from this dissertation work was a sample preparation microfluidic device and a rapid and sensitive IgM immunoassay platform for diagnostic testing at the point of care, particularly applicable for the developing world. |
