Preparation And Characterization Of Magnetic-fluorescent Composite Nanoparticles

Magnetic-fluorescent nanomaterials with integrated properties are the hotpot in a variety of multi-functional nanomaterials, and widely used in biomedical fields. Magnetic-fluorescent nanomaterials combine magnetism and fluorescence into one entity and have found potential applications in bioimaging, cell labeling, drug delivery, tumor hyperthermia and so on. This thesis focuses on the design, fabrication and characterization of magnetic-fluorescent composite nanoparticles that exhibit favorable magnetism and fluorescence simultaneously.Herein, two types of magnetic-fluorescent nanomaterials, Fe₃O₄/ZnS composite nanoparticles andγ-Fe₂O₃/ZnS composite nanoparticles, were fabricated and their magnetic-fluorescent properties and cytotoxicity were characterized. Rare-earth ions were doped into the prepared composite nanoparticles to obtainγ-Fe₂O₃/ZnO:Eu and Fe₃O₄/ZnS:Tb composite nanoparticles. The effect of rare-earth doping on the fluorescent properties of the composite nanoparticles were studied in details.(1) Magnetic Fe₃O₄ nanoparticles were synthesized by a coprecipitation method followed by modification with sodium dodecyl sulfate (SDS). Fe₃O₄/ZnS composite nanoparticles were prepared via in situ approach. The composite particles have spherical morphology and are uniform in size with diameters ranging from 70 to 100 nm, and show satisfied magnetic and fluorescent properties. In vitro cytotoxicity of the Fe₃O₄/ZnS composite nanoparticles was tested by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] method on Hela cells and the results indicated favorable biocompatibility of the Fe₃O₄/ZnS composite nanoparticles. Successful labeling of hepatocellular carcinoma (HepG2) cells was accomplished by the Fe₃O₄/ZnS composite nanoparticles.(2) Sphericalγ-Fe₂O₃/ZnS composite nanoparticles with uniform diameters of 100-200 nm were prepared by in situ approach and show favorable magnetic and fluorescent properties. MTT tests on human cervical cancer (Hela) cells were done with different concentrations ofγ-Fe₂O₃/ZnS composite nanoparticles and the results show that cell viability was not significantly affected by incubation in the presence of theγ-Fe₂O₃/ZnS composite nanoparticles where the viabilities remain at 73% even at high concentrations of 1.763μg/mL, indicating favorable biocompatibility of the composite nanoparticles.(3) Eu³⁺ doped ZnO (ZnO:Eu) and Tb³⁺ doped ZnS (ZnS:Tb) nanoparticles were prepared by sol-gel and coprecipitation method, respectively. XRD patterns demonstrated that the phases and crystal structures of ZnO and ZnS were not changed after rare earth doping. The presence of rare earth elements were identified by EDS analysis, which measured the atomic ratios between Zn element and Eu/Tb element within the doped products. Fluorescence measurements show that the emission peaks characteristic of rare earth ions (i.e., Eu³⁺ and Tb³⁺) accomplish maximum intensity when the atomic doping concentration is 3%. Subsequently,γ-Fe₂O₃/ZnO:Eu and Fe₃O₄/ZnS:Tb magnetic-fluorescent composite nanoparticles were fabricated by encapsulatingγ-Fe₂O₃ and Fe₃O₄ nanoparticles into ZnO:Eu and ZnS:Tb nanoparticles, respectively, and the fluorescent properties of the prepared products were characterized by fluorescence spectrophotometer.