| Microfluidics technology aims to revolutionize chemical and biological analysis by miniaturizing and integrating analysis steps such as sample preparation, fluid handling, separation, and detection into compact and inexpensive devices that consume very small reagent volumes in comparison to conventional techniques. Since many analytical operations, including chromatography, solid phase extraction, and enzymatic reactions, rely on the interaction of analyte with surfaces, solid support materials are needed to improve device performance and efficiency. Porous polymer monoliths are attractive for microfluidics applications due to their high surface area to volume ratio, simple in situ preparation, and the wide range of possible physical and chemical properties. This dissertation describes the implementation and integration of polymer monoliths in microfluidic systems for bioanalytical applications.; The first chapter introduces polymer monoliths as well as alternative technologies for incorporating solid supports within microfluidic systems before reviewing the various microfluidic applications of polymer monoliths. Next, a procedure enabling the covalent attachment of polymer monolith to the walls of polymeric microfluidic devices is described in Chapter 2. This procedure prevents the formation of voids at the monolith-channel interface, which is otherwise a significant problem due to the shrinkage of monolith during the polymerization process. In Chapter 3, the walls of cyclic olefin copolymer microfluidic chips are surface modified with a hydrophilic layer using a photografting process in order to prevent nonspecific adsorption of protein. This procedure is extended and improved for the protein-resistant, hydrophilic surface modification of polymer monoliths in Chapter 4. Control of protein adsorption is critical in microfluidic devices and on polymer monoliths that are to be used for the analysis of biological samples in order to prevent sample loss, degradation of resolution in separations, and difficulties with accurate quantitative analysis. Finally, in Chapter 5 these techniques are combined and utilized to prepare spatially-localized multi-enzyme polymer monolith enzymatic reactors. Sequential multi-enzymatic reactions were demonstrated using the stepwise preparation of two- and three-enzyme systems. In addition, these microreactors made possible the in situ analysis of the immobilized enzyme kinetics. The techniques developed as a part of the work summarized in this dissertation should enable greater use of polymer monoliths in bioanalysis as well as their integration in more complex analytical systems. |
