The Study Of Optical Bio-sensing And Imaging Based On The Localized Surface Plasmon Resonance Of Gold Nanoparticles

Nanophotonics is a cutting-edge subject merging both nanotechnology and advanced photonics technology. In the last decades, it has been providing new perspectives and solutions for biomedical research, because of its unique advantages and great potential. As one of the most widely used materials, gold nanoparticles have many interesting optical properties and related applications. In this thesis, we are going to discuss two kinds of gold nanoparticles, i.e., gold nanospheres and gold nanorods. We will introduce their synthesis, surface coating and conjugation methods in detail. And we will also focus on their localized surface Plasmon resonance (LSPR) and a great bunch of relevant research work on optical biosensing and bioimaging. Details as following:1. The synthesis methods of gold nanospheres and gold nanorods are introduced. And they are coated with several kinds of polyelectrolyte, PEG or silica to improve stability. Different ways of particle characterization are introduced, including UV-vis spectra, TEM and zeta potential. The optical properties of gold nanoparticles also have been worked on, such as LSPR, Rayleigh scattering and localized electromagnetic enhancement.2. A streptavidin sensor has been designed based on the LSPR effect of gold nanoparticles. In this design, gold nanoparticles modified with biotins are immobilized on glass with the help of bovine serum albumin. Streptavidin molecules in the analyte solution will be attached on the surface of gold nanoparticles because of the specific conjugation between biotin and streptavidin. By checking the red shift of the LSPR peak, a limit of1nM streptavidin can be acquired.3. Gold nanoparticles’ dark field scattering imaging and its applications in labeling cells cytoplasm and nucleus are discussed. By combining TIRF module and inverted microscope, we have also accomplished the evanescent field excited Rayleigh scattering imaging, which shows great advantage in studying cells’membrane activities.4. Gold nanorods are excited by ps pulse laser and generate several nonlinear emissions, e.g., two-photon luminescence (TPL), second harmonic generation (SHG), and coherent anti-Stokes emission (CAS). We also dig into gold nanorods’CAS signal properties, and get the CAS imaging of gold nanorods’assemblies on silicon wafer to prove its potential in optical bioimaging.5. We also accomplish the application of surface enhanced Raman scattering (SERS) in three levels, i.e. molecules, cells and in-vivo detecting and imaging. Based on the enhanced electromagnetic field, the Raman scattering of dye molecules attached on the surface of gold nanorods will be greatly enhanced. According to this principle, we have designed a multilayered-polymer-coating Raman probe PAH-PSS-Dye-GNRs, and achieved the multimodal optical imaging of cancer cells. We also have designed a fluorescence/Raman probe PEG-Dye-GNRs, which has been sucessfully used in rats’ in-vivo fluorecence imaging and Raman detecting and turmor targeting and so on.6. A Raman microscopy system based on a785nm semiconductor laser and an inverted microscope has been built. Combining with TIRF module, we also get Raman signal with evanescent field excitation.