Bioimaging Application And Biological Effects Of Core@Shell Magnetic Nanoparticle Assemblies

Magnetic nanomaterials are important inorganic functional biomaterials. Recently, magnetic nanoparticle assemblies have attracted great attentions owing to their higher saturation magnetization, high magnetic anisotropy, chemical stability and multiple-pose applications. Especially, attempts to prepare the nanomaterials with higher magnetic property and enhancement in their biocompatibility for clinical application are among the hot research topics in this field. This dissertation focuses on design and preparation of magnetic nanoparticle assemblies with good biocompatibility, and their biological effects. The main results are briefly summarized as follows:1. By microwave-assisted synthesis, a series of NiCo magnetic nanoparticle assemblies with different proportion of nickel and cobalt in a large amount can be prepared. These nanoparticle assemblies are made of magnetic nanocrystals with diameter of approximately30nm. Magnetic property, especially the saturation magnetization of the alloy changes with the proportion of the Ni and Co. Furthermore, the autophagy effect induced by NiCo magnetic nanoassemblies has been reported, which linearly increases with the rise of content of nickel. In addition, with the increase of content of cobalt in the alloy, the biocompatibility will increase. Consequent suppression of autophage effect also dramatically decreases the cytotoxicity of nanoalloys, so appropriate regulation of autophage could help to realize the utilization of those magnetic nanomaterials in medical diagnose.2. Core@shell structured NiCo alloy nanoassemblies with mesoporous silica layer have been designed and prepared. Due to the capsulation of silica, the dispersibility, water-solubility, stability and biocompatibility of the core/shell nanoassemblies are much improved. The magnetic core displays well spin-spin relaxtion (T2) magnetic resonance imaging (MRI) ability, while silica shell can provide a higher storage capacity for fluorescent molecular and drug with sustained drug release kinetics. The nanoassemblies can reach cancer cells rapidly and accurately with the help of external magnets. This nanocomposite has been applied to theranosis, accurately targeted tumor cells as well as drug therapy.3. By usi ng carbonaceous nanospheres as template, an etchi ng-f ree method has been developed to synthesize Y2O3:Yb3+/Er3+hollow nanospheres. Nanocrystals with core-shell structures are effective in both reducing amount of expensive lanthanide elements and incorporating drug molecules for chemotheraphy. Furthermore, surface modifications by PEG greatly increased the biocompatibility and dispersity of the hollow spheres. In addition, PEG prolong the circulation time of nanomaterials in vivo effectively for therapeutic applications. This novel hollow material displays perfect potentials in drug delivery and in vivo imaging. Meanwhile, the actual distribution and metabolism of nanomaterials in mouse after injection has been investigated, and no hemolysis or other immune response are observed, which give promise of the further clinical application of this kind of nanomaterials.