Engineering the Optical Properties of Gold Nanostructures for Biomedical Applications

This research investigated the synthesis and optical properties of Au nanostructures with an aim to use them as imaging agents and photothermal transducers for the diagnosis and treatment of cancer. I have produced Au nanocages with hollow interiors and porous walls using the galvanic replacement reaction between Ag nanocubes and AuCl4-. I have engineered these Au nanocages to have localized surface plasmon resonance: LSPR) peaks in the near-infrared region with strong absorption. These optical properties allow for the imaging of biological tissues at deeper penetration and the photoablation of cancer. By replacing AuCl4- with AuCl2-, Au nanoframes were developed. With a series of discrete dipole approximation calculations: DDA), I illustrated how the edge length and ridge thickness of the nanoframe can affect the LSPR peak. I validated the calculated predictions by experimental measurements. I functionalized the surface of the Au nanocages with antibodies via Au-thiolate chemistry to target cancerous cells. The photoluminescence from Au nanocages provided a simple and convenient way to evaluate their in vitro targeting capability using two-photon microscopy. This mode of imaging can be used to quickly screen the interaction between Au nanocages and cells, as well as evaluate the distribution of Au nanocages in tissue for ex vivo and in vivo studies. I also quantified the photothermal effect of the Au nanocages targeted to cancer cells using flow cytometry coupled with propidium iodide staining. In addition to Au nanocages and nanoframes, I have synthesized Au microplates using a biological macromolecule, bovine serum albumin: BSA), as the reducing agent. I exposed the reductive hydroxyl groups in the protein by unfolding the structure at an elevated temperature, under an acidic condition, and in the presence of ions