Study On The Synthesis,Surface Modification Of Ln³⁺ Co-Doped Upconversion Nanoparticles And Its Application

Upconversion luminescent nanomaterials, which can convert near infrared light into visible light through a multi-photon mechanism, with low energy light, high and stable luminous intensity, high resistance to photobleaching, high tissue penetration ability and low toxicity allowed it to get a strong development in tumor imaging diagnosis and therapy. Because of its unique optical property and chemical property, upconversion luminescent nanoparticles have been successfully applied in fluorescence imaging, and also did research on magnetic resonance imaging. In this dissertation, we synthesize Gd³⁺ ion doped UCNPs which modified by BSA-Gd with water solubility and biocompatibility and also enhance its practical MRI performance. The in vivo behaviors and toxicology of those UCNPs are studied as well. On the other hand, we designed core/shell UCNPs to improve its fluorescence intensity for fluorescence imaging. Based on this, the main contents as follows:1. Three types UCNPs were synthesised via thermal decomposition procedure. Through the DLS and TEM, the result shows that the final nanopartilces are all in 30 nm with good crystallinity. With the application in bioscience, we modified these UCNPs with BSA-Gd for improving its biocompatibility and relaxation rate, and the group modified by pure BSA considered as contrast. From the results, we know that modification of UCNPs with pure BSA or BSA-Gd was successful, with in vitro magnetic relaxation rate and MRI, we found the r1 and r2 may be not reflact the realistic MRI and the MRI performed enhancement with the concentration incresing. The cell cytotoxicity, pharmacokinetics and H&E results indicated the UCNPs had good biological compatibility. The results concluded the nanoparticles we designed could be a good choice as contrast agent for magnetic resonance imaging.2. Based on the application of UCNPs in bioscience for its unique optical property and chemical property, and the work above, we found, the fluorescence intensity of UCNPs would decrease sharply after modifying, which limits its application in fluorescence imaging. On the basis of successiveion layer adsorption and reaction method, we fabricate the core/shell UCNPs through one pot successive layer-layer strategy, with the contrast of the core/shell UCNPs synthesised by traditional thermal decomposition procedure. The results show the UCNPs synthesised by the one pot successive layer-layer strategy performs high dispersion and high crystallinity, and its fluorescence intensity stronger than the UCNPs synthesised by thermal decomposition procedure. After modification with PMAO, the fluorescence intensity did not decrease sharply. So the core/shell UCNPs synthesised by the one pot successive layer-layer strategy can enhance the fkuorescence intensity remarkablely.