| With the development of the society, health problem has attracted much attention. Bioimaging has wide applications in medical research, clinical diagnosis, and therapy, and it has been an important part of modern medicine. Compared with the commonly used imaging methods, like X-ray, acoustic, and magnetic resonance imaging (MRI), optical imaging is very promising as it has inherent advantages like high resolution, no radiation pollution, and it can been applied for various objects. In this thesis, focusing on some optical effects, a lot of work on bioimaging was introduced, with the help of some nanoparticles as the imaging agent. The work was mainly about:1. Quantum dots with high quantum yields were used as imaging contrast for single-photon fluorescence imaging. The hydrophobic CdSe/ZnS core shell QDs were coated with SiO2 shell and carboxyl group (-COOH) to be hydrophilic, and they would be compatible with the bio-environment. They were uniform, stable, and mono-dispersed after coating. The QDs were further conjugated with transferring, and HeLa cells were targeted for fluorescence imaging. By contrast experiments, it was proved to be a type of specific targeting, and this would be helpful in cancer cells diagnosis and treatment.2. The aggregation-induced emission (AIE) dyes with bright fluorescence were applied for two-photon luminescence (2PL) imaging. The AIE properties of BT3 molecules were characterized and they were encapsulated into nanoparticles. BT3 nanoparticles were found to give red fluorescence, with large Stokes shift, and this would be very benefit for bioimaging. BT3 nanoparticles were found to have a large two-photon absorption (2PA) cross section of 2.9×106 GM at 1040 nm, which was larger than its values at the wavelengths ranges from 770-860 nm, and this was also larger the values of many commercial dyes (like Rhodamine B). Also,1040 nm light was found to have better penetration ability than 800 nm light in bio-tissues. The biodistribution and clearance of BT3 nanoparticles in mice were also studied, and them were found to be mainly accumulated in the liver and can be cleared with metabolism. With the excitation of 1040 nm fs laser, mice injected with BT3 nanoparticles were applied for in vivo 2PL brain imaging. The blood vessels in the mouse brain could be viewed clearly, and an imaging depth of 700 μm was obtained. The combination of proper excitation wavelengths and AIE nanoparticles with larger 2PA cross section would be meaningful for future deep tissue imaging.3. Gold nanorods with good optical properties were utilized for nonlinear optical imaging. GNRs with varies aspect ratios were synthesized and were further coated with polyelectrolyte, SiO2 and PEG separately for different applications. Discrete dipole approximation (DDA) was utilized to simulates the absorption, scattering, and near-field characteristics of GNRs. The nonlinear response of GNRs under the near-infrared (NIR) fs laser excitation was recorded by a home-built optical system. GNRs were then applied for multi-channel nonlinear imaging of cancer cell, with its second harmonic generation (SHG), third harmonic generation (THG), and three-photon luminescence (3PL) signals,under the excitation of 1260 nm and 1580 nm fs laser separately. Images with good contrast were obtained on both excitation wavelengths and in both channels, and these results would be helpful in future in vivo nonlinear imaging with GNRs in the second and third optical tissue windows. |
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