Construct And Investigation Of Multifunction Upconversion Nanoplatform In Cancer Imaging And Therapy

Cancer is a very common disease but seriously threatens human life, because thecancer diagnosis is usually too late that always misses the best period for treatment.In our country, cancer has exceeded all the other disease and become the No.1causeof death. According to oncologist’s estimates, cancer cure rate might be able to reach80%-90%if it is possible to diagnosis and treatment the early cancer at millimeter（mm） level. Therefore, early diagnosis and treatment of cancer has become a majorproject in modern biomedical research. In recent decades, with the increasedunderstanding of the cancer grow process as well as the rapid development ofnanoscience and nanotechnology, lots of efforts have been carried out in this area,and series nanoplatforms have been proposed in the laboratory aiming for the earlycancer diagnosis and therapy, such as phospholipids vesicles, polymer nanomaterials,meso-porous silica nanoparticles, magnetic nanoparticles, semiconductor quantumdots （QDs）, as well as upconversion nanoparticles. These nanoplatforms with tumortargeting delivery properties have brought new hopes for the early diagnosis andtreatment of cancer.Rare earth ions doped upconversion luminescence nanoparticles （UCNPs） is a novel material that can absorb two or three longer wavelength low energy photonsand emit one shorter wavelength high energy photon. Compared with traditionaldown conversion fluorescent materials like organic dyes, semiconductor quantumdots （QDs）, UCNPs have series of unique advantages in biosensing and imaging asusing near-infrared light for excitation: deeper tissue penetration depth, lowerdamage to biological system, no background fluorescence noise, higher sensitivity inimaging, and no photobleaching effects etc. In addition, UCNPs themselves alsohave high chemical stability and low toxicity to biological systems. Therefore,UCNPs have shown great application prospects in biomedical research, especially incancer diagnosis and treatment. A lot of researches and explorations have beencarried out recently, including synthesis of nanoparticles, surface modification,biological functionalization, bio-toxicity, cell imaging, animal imaging,multimodality imaging, photodynamic therapy, as well as imaging-guided cancertreatment launched et al. However, there are still some issues among those reports,such as poor solubility and stability of nanoparticles in water phase, poor stability ofsurface functioned biomolecules, poor target efficient in tumor, and so on.In this thesis, high quality hexagonal phase NaYF₄:Yb³⁺,Er³⁺upconversionnanoparticles with unique size distribution, good crystalline property and highluminescent efficiency are firstly synthesized based on high temperaturedecomposition method. Then ligand exchange process is carried out to transfer thehydrophobic nanoparticles into hydrophilic, which endow the NaYF₄:Yb³⁺,Er³⁺with excellent water solubility and biocompatibility. Based on this, we are able tocovalent coupling different biomolecules with UCNPs for further biomedicalresearch: constructed a multifunction upconversion nanoplatform and achieved invitro cancer cell target imaging and therapy; developed a in vitro three-dimensionaltumor spheroids culture method and specificly labeled them with antibodyfunctioned upconversion nanoparticles. Moreover, some preliminary issuesinvolving in upconversion luminescence imaging also interest us, by using MonteCarlo simulation method, we penetrating researched the process of excitation light and converted emission light in tissue.. The main results are summarized below:（1） Using high-temperature decomposition method, hexagonal phaseNaYF₄:Yb³⁺,Er³⁺are synthesized which uniform size distribution, goodcrystallzation and high upconversion luminescence efficiency. And using smallmolecular amino acid （AEP） as the ligand, we successfully transferred theupconversion nanoparticles from oil phase to aqueous phase, rendering upconversionnanoparticles with very good water-solubilities and biocompatibilities.（2） Based on the AEP capping on nanoparticles, a covalent coupling strategy wasdeveloped to assemble photosensitizer molecules of rose bengal （RB）, targetingmolecules folic acid （FA） and polyethylene glycol molecules （PEG） ontoNaYF₄:Yb³⁺,Er³⁺upconversion nanoparticles surface, construct a multifunctionalplatform that can be used for simultaneous target cancer cell imaging andphotodynamic therapy. The amount of photosensitizer loaded, the efficiency of energytransfer and singlet oxygen yield are greatly improved. We use humanchoriocarcinoma JAR cell line as a model to research the biocompatibility, targetproperty, and PDT efficacy of the upconversion nanoplatform.（3） Using human breast cancer cell line MCF-7, we develop an in vitro3-dimensional multicellular tumor spheroids culture method. compared withtraditional2-dimensional cell culture, tumor spheroids can better mimic the realtumor. According to EDC method, we construct anti-ER-α antibody functionedNaYF₄:Yb³⁺,Er³⁺nanocomples, and achieve the target upconversion luminescenceimaging of3-dimensional MCF-7tumor spheroids.（4） Using Monte Carlo method, we simulate the light propagation process inusing upconversion luminescence nanoparticles for cancer imaging andphotodynamic therapy. This is composed of two parts, firstly we simulated thefluence distribution and penetration depth of980nm near-infrared excitation lightinto the tissue; and then we simulate the unconverted luminescence round threedifferent wavelength540nm,650nm and800nm attenuation in the tissue. It revealsthat the Tm doped UCNPs with800nm has the deepest penetration depth. In summary, this thesis carry out an in-depth research in rare earth dopedluminescent nanoparticles synthesis, surface modification and functionalization, andtarget cancer cell imaging and therapy etc. All these contributions are of greatimportance in implementation early cancer diagnosis and therapy.