Design and development of surface plasmon resonance imaging microfluidic assays

Abstract

This dissertation focuses on the design and development of SPR-imaging microfluidic assays to quantify nanomolar concentrations of small molecules (cortisol and phenytoin) in saliva for a point-of-care medical diagnostic. Microcontact printing, as a method to immobilize proteins on gold surfaces, was characterized with SPR-imaging, XPS, and XPS-imaging. Computational models of a standard microfluidic flow assay, an indirect immunoassay, and the concentration gradient immunoassay were developed to achieve a deeper understanding of the mass transport of analytes within a microchannel as well as to explore methods to improve the sensitivity of a microfluidic flow assay. The models showed strong qualitative agreement with experimental results. A microfluidic mixer---the herringbone channel---was incorporated in a microfluidic assay. The surface binding profile of a protein was significantly altered with this geometry. The surface binding profile was confirmed with SPR-imaging experiments. The model did not indicate an increase in the rate of binding of the protein to the surface of the herringbone microchannel when compared to a straight microchannel. Experimentally, at distances further downstream than that explored by the computational model, there was a modest increase in the rate of binding of the protein to the surface, suggesting that the herringbone geometry requires longer distances to significantly increase the rate of binding of a protein to a surface.