Nanoscale Biosensing: Fabrication and Characterization of Electrochemically Deposited Nanostructured Arrays and Single Nanoparticle Surface Plasmon Resonance Microscopy

The work presented in this dissertation covers two types of nanomaterials (nanostructured arrays on surfaces and nanoparticle suspensions) with a unified focus on biosensing applications utilizing surface plasmon resonance (SPR), a surface sensitive phenomenon that occurs at the nanoscale. The first part of the dissertation describes the fabrication of lithographically patterned and electrochemically deposited large-scale arrays of nanorings and split nanorings. The fabrication and characterization of nanoring arrays made from a host of materials such as Ni, Au, Co, and polydopamine are discussed. Additionally, the fabrication of split nanoring arrays with potential applications as a tunable dichroic is explained. The application of plasmonic gold nanoring arrays as a biosensor to detect DNA hybridization with detection capabilities down to 50 pM of DNA follows. The next part of this dissertation shifts focus from nanostructured surfaces to the detection of nanoparticles in suspension using surface plasmon resonance microscopy (SPRM). Specifically, polymeric hydrogel nanoparticles that have been engineered to bind the hexacosa peptide melittin is studied. Point diffraction patterns in sequential real-time SPRM differential reflectivity images are counted to create digital adsorption binding curves of single 220 nm diameter hydrogel nanoparticles from picomolar nanoparticle solutions onto alkanethiol-modified gold surfaces. The SPRM responses from the adsorption of hundreds of individual hydrogel nanoparticles are quantified to measure the loading of melittin, a potential therapeutic compound, into the nanoparticles. Additional bulk fluorescence measurements of melittin uptake into the hydrogel nanoparticles are used to correlate the maximum signal observed by SPRM to the incorporation of approximately 65,000 molecules into each 220 nm hydrogel nanoparticle, corresponding to roughly 4% of its volume