Preparation Of Near Infrared Luminescent Rare Earth Doped Nanomaterials And Their Application In Tumor Targeting Fluorescence Imaging

Rare earth doped nanoparticles(NPs)have been widely used in fluorescence display,laser,information transmission and other fields,and they also have great application prospect in biological imaging.Imaging technology can visually display the cell activity and lesion evolution in living animals,which is a powerful means of biological detection and diagnosis technology,and is being more and more widely used in biological fields.The rare earth doped nanoparticles exhibit remarkable advantages in biofluorescence imaging due to their high fluorescence intensity,low cost,rapid feedback,high sensitivity and radiation-free properties.In tumor diagnostics and treatment,fluorescence imaging is widely used to monitor the interactions between drug molecules and tumor cells,especially NIR fluorescence imaging,which has negligible tissue scattering,absorption,self-fluorescence and extremely high signal-to-noise ratio,can monitor the real-time dynamic process in biological tissues in vivo.However,besides the ability of improving the fluorescence intensity,fluorescent NPs must have good biocompatibility and targeting ability for lesions or tumors,which is the key for NPs to efficiently accumulate in the lesions or tumors and greatly improve the fluorescence signal intensity during biological imaging.In order to solve the above problems,the preparation,characterization,modification and biological imaging application of the rare earth doped NPs with near-infrared excitation and near-infrared emission are investigated in this thesis.The research contents and results mainly include the following three parts:(1)A NIR excitation-NIR emission fluorescent nanoprobe K₅NdLi₂F₁₀(KNLF)was designed and synthesized by liquid phase method.Under 808 nm excitation,KNLF NPs exhibited high fluorescence emission at 1056 nm and its quantum yield and the lifetime of KNLF NPs reached 13.3% and 130 ?s respectively,which is significantly higher than that of the commercial dye molecular biological imaging probe.The fluorescence penetration depth of KNLF NPs in the phantom and fresh pork tissues reached 3.5 and 2 cm respectively,showing a better tissue penetration ability than the traditional up-conversion materials and quantum dots materials.Thefluorescence spectra showed that the three dispersions(deionized water,PBS,FBS)of KNLF could maintain the fluorescence intensity above 60% of the initial value after continuous irradiation for 2 h with a 70 m W/cm² 808 nm laser.It can be used for subcutaneous high-quality(signal to noise ratio>10:1)fluorescence imaging of living mice.Study on the toxicity and in-vivo bio-distribution of the KNLF NPs indicated the material has high biocompatibility and negligible cytotoxicity.After that,the tumor imaging model of tumor bearing mice was constructed.Under the enhanced permeability and retention(EPR)effect,the non-specific accumulation of KNLF nanomaterials in the tumor site was realized by tail vein injection,thus the preliminary fluorescence labeling and localization of tumor cells could be carried out.This indicates that KHLF is promising to provide an early and efficient detection and diagnosis method for tumors in future clinical applications.(2)A novel biocompatible fluorescent K₅HoLi₂F₁₀(KHLF)nanoparticle with 808 nm excitation and 887 nm emission was prepared by an optimized hydrothermal method.The nanoparticles have high near-infrared fluorescence emission efficiency and excellent luminescence stability.The fluorescence intensity of KHLF powder and dispersions can still maintain 95.12% and 95.02% of the initial intensity under the condition of 2-h continuous irradiation of 808 nm laser with the power density of 1W/cm².A long-term fluorescence monitoring model(1 h-14 d)in vivo of mice was constructed.The real-time detection of fluorescence signal distribution and metabolic process in mice was realized by using KHLF nanomaterials.The highest imaging signal-to-noise ratio(SNR)in vivo was up to 14:1,which is in the leading level in the field of in vivo imaging.This material showed low toxicity,high imaging sensitivity and rapid metabolism after imaging,so it has great potential in noninvasive imaging monitoring and diagnosis in vivo.The material also had better photothermal effect.When the KHLF dispersions(15 mg/mL)was continuously excited by 808 nm lasers(4 W/cm²)for 4 min,its temperature exceeded 50?,which is expected to be used as an efficient photothermal medium in tumor treatment.(3)The KHLF NPs were modified with 3-aminopropyltriethoxysilane(APTES)by surface modification method.Folic acid(FA)was covalently attached to thesurface of the NPs,enabling them the good water-solubility and tumor targeting ability for Hela cells.It could be seen from the subsequent fluorescence imaging experiments that the fluorescence intensity of FA modified NPs in aqueous solution can still maintain more than 80% of that without modification,which can meet the requirements of imaging intensity for subsequent in vivo tumor targeting.Finally,the tumor targeted imaging model of Hela tumor bearing mice was established,and different control groups were designed for fluorescence imaging experiments.The results showed that FA-NPs can accurately target the Hela tumor cells and produce strong fluorescence signals,so it can realize the early detection and diagnosis of Hela cells in mice.