Date of Award
8-2022
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Chemistry
Committee Chair/Advisor
Dr. Jeffrey N. Anker
Committee Member
Dr. George Chumanov
Committee Member
Dr. Jason D. McNeill
Committee Member
Dr. Joseph W. Kolis
Abstract
This dissertation discusses the development of plasmonic and X-ray luminescence nanoparticles (~100 nm) to use in bioimaging and sensing applications. The nanoparticles have interesting optical properties compared to their atomic levels and bulk materials. The optical properties of nanomaterials can be controlled by changing size, shape, crystal structure, etc. Also, they have a large surface area that can be functionalized with biomolecules. Therefore, the optical properties and biofunctionalized nanomaterials are useful in biomedical applications such as targeted drug delivery, bioimaging, and sensing. The overall theme is to use nanoparticles with interesting optical properties compared to their atomic levels and bulk materials to understand and control size/shape-dependent optical properties and crystallinity. Here, we discuss nanomaterials' optical properties and biofunctionalization in three sections, 1) size/shape-dependent optical properties of plasmonic nanoparticles, which we develop a simple and robust mechanical approach to prepare plasmonic nanoparticle arrays, 2) X-ray optical luminescence of X-ray luminescence nanoparticles which depends on crystal defects and amount of dopants by synthesizing them and enhancing their intensity to use them in high-resolution imaging, 3) biofunctionalization of gold and X-ray luminescence nanoparticles to develop immunoassays. Chapter two describes the development of a simple, mechanical approach to preparing plasmonic nanoparticle arrays and transferring them onto a thin film. Plasmonic nanoparticles can absorb and scatter visible range light depending on their size, shape, and environment, and unlike fluorescence dyes, they do not photo-bleach. Plasmonic nanoparticles and array of nanoparticles have many applications including in bioimaging and sensing. The current methods to develop nanoparticle arrays and transfer them onto thin films are complex, time-consuming, and expensive. Here, we report a simple technique to generate patterns of gold and silver nanoparticles with controlled shape and shape-dependent optical properties. The pressure was applied to nanoparticles on a glass slide to convert nanospheres (diameter ~ 90 nm) to nanodiscs (diameter ~180 nm). Metal stamps and glucose deposits were placed on nanoparticles before applying pressure to generate patterns. The change in nanoparticle shape causes their localized surface plasmon resonance wavelength to red-shift. Also, we developed a method to remove undeformed nanoparticles using scotch tape and transform nanoparticle patterns into a flexible polymer film. Like plasmonic nanoparticles, X-ray luminescence nanophosphors can be used as an optical contrast agent in biomedical imaging and optical biosensors. They generate visible light through tissue when irradiated with X-rays. However, the sensitivity of these applications depends on the intensity of emitted visible light, and it is important to investigate methods to enhance its intensity. Herein, we describe the synthesis of X-ray scintillating NaGdF4:Eu and Tb nanophosphors via co-precipitate and hydrothermal methods, enhancing X-ray excited optical luminescence. The brightest particles were obtained using hydrothermal synthesis, and thermal annealing enhanced X-ray luminescence intensity. However, annealing above 600 °C changes the chemical structure to NaGd9Si6O26:Eu, which results in a shift in the X-ray luminescence spectra. Further, we demonstrated that the particles generate light through tissue and can be selectively excited using a focused X-ray source for imaging and spectroscopy. The fourth chapter brings plasmonic and X-ray luminescence particles together to develop immunoassays. Here, we describe a design and development of a gold nanoparticles-based lateral flow assay (LFA) to detect SARS-CoV-2 antibodies in human saliva and a proof of concept to develop an immunoassay using gold nanoparticles and X-ray luminescence nanoparticles. Gold and X-ray luminescence particles were functionalized with receptor binding domain protein and human anti-spike IgG, respectively. Our preliminary studies show the ability to develop the LFA to detect SARS-CoV-2 antibodies in human saliva, an immunoassay using RBD functionalized gold nanoparticles, and anti-spike IgG functionalized Gadolinium oxysulfide microparticles. The X-ray luminescence decreases by a factor of 1.8 due to light absorption when attaching gold nanoparticles to Gadolinium oxysulfide microparticles. This can be developed as an implantable immunoassay to quantify biomarkers in vivo locally and continuously. Chapter five includes a separate study that is not based on nanoparticles-based bioimaging and sensing. However, it discusses a behavioral analysis to discover and understand the X-ray stimulated behavior of Caenorhabditis elegans. Chapter six provides a conclusion and discusses possible future work for each chapter.
Recommended Citation
Ranasinghe, Meenakshi, "Development of Plasmonic and X-Ray Luminescence Nanoparticles for Bioimaging and Sensing Applications" (2022). All Dissertations. 3095.
https://open.clemson.edu/all_dissertations/3095
Author ORCID Identifier
0000-0002-0858-1298