| In recent years, microfluidic biosensors have been increasingly implemented in clinical diagnostics for point-of-care monitoring of prescription drug levels and disease detection. These devices have the potential advantages of increased portability and reduced assay times and reagent volumes. However, despite numerous benefits over traditional centralized laboratory-based assays, the sensitivity of POC diagnostic tests remains a valid concern. Improvements to the assay detection limit, such as through the use of signal amplification schemes based on enzyme-catalyzed precipitation reactions, have the potential to expand the reach of POC diagnostics.;In response to this need for improved detection limits, two signal amplification schemes were developed, including a novel lateral amplification format involving electron transfer between redox-active enzymes and the gold sensor surface. These amplification schemes, developed on the surface plasmon resonance microscopy platform, sought to improve the assay limit of detection by increasing the magnitude of the signal associated with analyte binding. The enzyme horseradish peroxidase and the precipitating colorimetric substrate 3,3',5,5'-tetramethylbenzidine were employed to provide rapid and significant enhancement of the SPR signal. The mechanisms and quantitative potential of these amplification schemes were investigated, and computational models of the HRP/TMB reaction system were developed.;A piezoelectric inkjet printing tool, which enabled multi-analyte patterning of gold surfaces for the development of microfluidic bioassays, was also constructed and characterized. This surface patterning tool was used extensively in the enzyme-catalyzed signal amplification work. Both ethanol-based thiol solutions and aqueous protein solutions were patterned with a high degree of precision and flexibility.;Enzymatic signal amplification is an enabling technology with the potential to expand the utility of POC diagnostic devices to include low-concentration analytes and complex biological samples. Furthermore, the piezoelectric inkjet printing system developed in this research has widespread utility, as it was shown to be capable of generating high-quality, localized, and customizable sub-millimeter patterns in a nonfouling background for multi-analyte bioassay development. Thus, the development of these tools has the potential to advance SPR-based point-of-care microfluidic diagnostics through improvements in the assay detection limit and the availability of a versatile surface functionalization method. |
