Gold nanoparticles in DNA-directed nanostructure assembly and surface plasmon resonance biosensors

This thesis describes the use of metal nanoparticles as building blocks in materials applications and investigates their potential as amplification tags in multiplexed assays. Chapter 2 describes the temperature-programmed assembly of DNA:Au nanoparticle conjugates. The effects of DNA surface coverage and DNA orientation on the conjugate melting properties were investigated. It was found that the surface coverage of DNA on the Au nanoparticles depends on the sequence length, and on whether the DNA strand is attached to the Au particle through its 5' or 3' end.; In Chapter 3 the effect of macromolecular crowding on DNA-modified nanoparticles by aqueous polymer solutions was investigated. The interface formed by two aqueous polymer solutions may provide a biocompatible 2-D scaffold for bio-directed assembly. The effect of polymer concentration and polymer molecular weight on the thermodynamics of DNA-.Au conjugates was studied for solutions of poly(ethylene glycol) (PEG) and dextran. It was shown that solutions of PEG have a strong stabilizing effect on the DNA:Au aggregates, while dextran has a much smaller stabilizing effect.; In Chapter 4, a new wet-chemical method is described for the preparation of high quality surface plasmon resonance (SPR) active metal films. The electroless plating of Au onto colloid monolayers is demonstrated as a viable approach to generate inexpensive high quality thin metal films. The effects of colloid surface coverage, and exposure time to the plating solutions were investigated. It was found that higher quality films were obtained using higher surface coverage monolayers, as the particles coalesced into a continuous film earlier in the plating process.; In Chapter 5, particle-amplified surface plasmon resonance was investigated as a possible method for performing multiplexed bioassays using multiple probes analogous to fluorescence microarrays.{09}The unique optical and electronic properties of metal nanoparticles and their ability to couple electronically to metal films may provide a method to detect different particle populations in a mixture of particle types using SPR. The size dependent SPR reflectivity was determined using imaging SPR. It was shown that the change in reflectivity for 42-nm particles is much greater than for 12-nm particles given similar surface coverages. (Abstract shortened by UMI.)...