Gold nanorods: Applications in chemical sensing, biological imaging and effects on 3-dimensional tissue culture

Gold nanoparticles have attracted great interest in the last decade for applications in biochemical detection, imaging, and therapeutics, due to their useful optoelectronic properties. Interest in this area has recently focused on engineering the surface of the nanoparticles, because of the ease in which the charge, functionality, and reactivity of the surface can be altered. This dissertation will focus on the applications of surface-engineered gold nanoparticles in chemical detection and biomedical imaging, and look at the effects surface modified gold nanorods have on the behavior of cardiac fibroblasts in tissue culture.;As an alternative to solution-based techniques in Raman spectroscopy, we have found that a sandwich architecture in which a surface assembled monolayer (SAM) of 4-mercaptobenzoic acid (4-MBA) is sandwiched between a 100 nm thick gold substrate and electrostaticaly immobilized gold nanocubes allows for more reproducible data as well as enhancement factors up to 1013. The sandwich architecture creates a large electromagnetic field in the area where the 4-MBA molecules reside causing the characteristic vibrational modes of 4-MBA to appear. We have also moved out of the realm of chemical sensing and have used our gold nanorods as point sensors to monitor the mechanical properties associated with mechanotransduction.;Cell behavior in the presence of nanomaterials is typically explored through simple viability assays, but there is mounting evidence that nanomaterials can have more subtle effects on a variety of cell functions. Numerous studies have documented the cellular uptake and cytotoxicity of gold nanoparticles in different cell types, but very little is known about how nanoparticles affect cellular function. We have shown that gold nanorods in a collagen thin film can be used to measure the local mechanical fields near and between living cells as they assess, adapt, and rearrange their environment. We have also found that gold nanorods in 3-D tissue culture interfere with the cardiac fibroblast-mediated remodeling of a collagen tissue construct. We have found several factors associated with the dose dependent decrease in cell-mediated collagen remodeling including the alteration of fibroblast phenotype, adsorption of cellular proteins needed for cell mediated remodeling, as well as a change in the mechanical properties of the tissue construct. The following chapters will detail the use of our gold nanomaterials as both biochemical and imaging agents, and discuss cell behavior in the presence of surface modified gold nanorods.