Development and application of a microspectroscopy system for plasmonic nanoparticle biosensing schemes

The specific detection of biomolecules within small volumes and at low concentrations is a significant challenge facing the fields of biology and medicine. There is a particular need for improved methods of detecting and analyzing proteins, which are important in understanding the functions of genes and accessing the immense potential of genetic therapies; discovering and evaluating disease biomarkers; developing new therapeutic agents; and identifying environmental pathogens. New biosensing approaches are required to address these needs.; This dissertation describes the development and application of a flexible and precise microspectroscopy system for the advancement of biosensing with plasmonic nanoparticles (NPs). The system provides high-resolution optical imaging and spectral measurement of individual NPs in a variety of experimental applications. Three such applications are presented.; The first application is the development of an analysis procedure for the rapid modeling of NPs' scattering spectra in the presence of a substrate. The procedure is based on the calculation of an effective refractive index environment, which depends on an empirically-derived weighting factor for the immersion medium above a substratebound NP. The effective index approach paves the way for the high-throughput optical modeling of NPs of other geometries, sizes, and materials.; The second application is an analysis of the experimental and analytical factors that influence uncertainty in the spectral analysis of individual plasmonic NPs. The described analysis provides a means of evaluating and optimizing detection thresholds, which is the key to detecting biomolecules at low concentrations, and points to the possibility of thresholds near the single molecule level.; The third application is the development of a spectroscopic approach to the determination of RI in live cells using immunolabeled gold nanospheres. The calculated mean RI indicates the nanospheres' environment within attoliter intracellular volumes. The development of this technique opens the door to the use of plasmonic NPs for high-resolution intracellular RI determinations and long-term monitoring of cellular dynamics.; The described applications have advanced the design and implementation of plasmonic NP biosensors. The advancements provided in these applications will lead to improved methods for the specific detection of various types of biomolecules in experimental, environmental, clinical, and industrial settings.