Functional Europium-Based Nanomaterials For Bioimaging

Due to the special photoluminescence properties, rare-earth luminescent materials as probes have attracted increasing attention. To date, rare-earth complexes and inorganic nanomaterials have been applied in bioimaging successfully. However, luminescent bioimaging with rare-earth materials as probes are still limited by the short excitation wavelength and dissociation of rare earth complex and short blood retention time of rare-earth nanomaterials. In this thesis, several europium-based nanoparticles have been synthesized and further applied in bioimaging in vitro and in vivo.1. Visible-light-excited and europium-emissive nanoparticles for high-contrast luminescent bioimaging in vivoEuropium(III)-based material has been considered as an ideal time-gated luminescence probe for bioimaging, but is still limited in cell imaging application. Here, a water-soluble, stable, highly-luminescent nanosystem (Ir-Eu-MSN) was developed by an in situ coordination reaction to form an insoluble dinuclear iridium(III) complex-sensitized-europium(III) emissive complex within mesoporous silica nanospheres (MSNs) which had high loading efficiency. Compared with the usual approach of physical adsorption, this in-situ reaction strategy provided 20-fold the loading efficiency (43.2%) of the insoluble Ir-Eu complex in MSNs. These nanoparticles in solid state showed high quantum yield of 55.2%, and the excitation window extended up to 470 nm. Morever, the Ir-Eu-MSN nanoparticles were successfully applied into high-contrast (SNR=9.9) luminescent lymphatic imaging in vivo under low power density excitation of 5 mW cm"2.2. Yolk-shell europium(Ⅲ) emissive nanoparticles for time-resolved luminescent detection of hypochlorous acidA yolk-shell nanocomposite (Ir-Eu-MSN@ysSiO2-Rb1) having europium emission has been synthesized and applied in time-resolved fluorescent detection of hypochlorous acid. This nanocomposite was consistent of Ir(Ⅲ)-Eu(Ⅲ) binuclear complexes functionalized mesoporous silica as a core and SiO2 as the shell, and further loaded with a HClO-sensitive dyes Rbl. This nanosystem could be used for detection HClO with high sensitivity and selectivity and further developed as time-resolved luminescence probe. Moreover, cell imaging experiments demonstrated that the nano-probe could monitor the distribution of ClO- within living cells.3. Radioactive 153Sm-doped EuOF nanocrystals (EuOF:153Sm) for dual-modal SPECT and X-ray CT imagingA ～5 nm PEG-EuOF:153Sm nanocrystals (PEG= poly(ethyleneglycol) bis(carboxymethyl)ether) combined with the radioactive and X-ray absorption properties were designed and synthesized. The biodistribution of the PEG-EuOF nanocrystals in living animals was studied by ex vivo radioassay, inductively coupled plasma-atomic emission spectrum (ICP-AES) analysis and in vivo SPECT imaging. The PEG-EuOF:153Sm had long blood retention time (blood half-life (t1/2)) of 4.65 h and were eliminated significantly through biliary/gastrointestinal pathway in vivo. Meanwhile, the PEG-EuOF was successfully applied for lymph node CT imaging. The studies of cytotoxicity and in vivo toxicity showed that the PEG-EuOF nanocrystals have relatively low toxicity.