Multicomponent Nanomaterials For Bio-imaging Based On Magnetic Assembly

As important inorganic functional biomaterials, magnetic nanomaterials have attracted great attentions in the field of magnetic separation of biomolecules, enzyme reaction, drug delivery and magnetic resonance imaging, due to their intrinsic magnetic properties and outstanding biocompatibilities. Recently, one hot topic on the research of magnetic nanomaterials is magnetic assembly of multiple building blocks to obtain magnetic nanocomposites with higher magnetic behavior and multifunctionality. This dissertation focuses on multicomponent nanomaterials for bio-imaging based on magnetic assembly, and the main results can be briefly summarized as follows:1. Multicomponent Ni7Co3 alloy-Au nanorings can be facilely synthesized at room temperature using metallic Ni7Co3 alloy nanorings as both reducing agent and sacrificial template in water. These novel alloy-Au hybrid nanorings are well biocompatible due to coating with poly(vinylpyrrolidone) and gold nanoparticles. When increasing the molar ratio of alloy to gold salt from 1:1 to 5:1, the number of gold nanoparticles loaded on the surfaceof alloy nanorings were found to be decreased, and their morphology was transformed from rod to particle, remaining the ring-like assemblies. Their saturation magnetization increased due to the ring-like assemblies, resulting in the enhancement of the signal intensity in spin-spin relaxation time (T2) weighted magnetic resonance imaging measurement. These alloy-Au hybrid nanocomposites can perform as multimodal imaging contrast agents for cancer cell diagnosis by two-photon fluorescent imaging and T2-weighted magnetic resonance imaging. In addition, their potential application for photothermal therapy was preliminarily investigated.2. A new kind of cobalt yolk/gold shell nanospheres with a superparamagnetic core left within hollow gold nanoshells can be synthesized. In addition,'peas in a pod'-like assemblies of them can be prepared under an external magnetic field. Owing to their cavitary structure and positivesurface potential, these hybrid yolk/shell nanostructures show excellent performance in applications as a nonviral vector forgene delivery and transfection.3. Interests drawn on inorganic hybrid nanomaterial have been increasing in recent decades due to its multifunction and simple preparation. Aiming to obtain a novel functional nano-composite, magnetization of the hydroxyapatite (HAP, Ca5(PO4)3(OH)) is an important issue. With previously reported HAP nano-willows by our group as templates, we report a facile method to manipulate magnetic assembly nanoworms. The HAP prepared by precipitation possess controlled morphology, size distribution and excellent bio-compatibility. With the coating of anionic polymer PSS, HAP could adsorb a large amount of iron precursor Fe(acac)3, then Fe3O4 NPs attached onto the surface of HAP crystal in situ in polyalcohol. The obtained hybrid magnetic nanoworms should be surface-modified by the multilayered coating of natural derived polymers for outstanding biocompatibility, and fit for magnetic resonance imaging. Assembled magnetic components could enhance its magnetic resonance imaging (MRI) contrast ability for the high concentration of magnetic material in a particular zone.4. Different from superparamagnetic iron oxide nanomaterials, Manganese (â…¡) oxide nanoparticles with paramagnetic property are emerging as a new type of sensitive T1-weighted MR imaging contrast agent. We report the first time on the one-step synthesis of highly water-soluble MnO nanocrystals capped with biocompatible polymer molecule using the fast microwave-assisted method in the polyalcohol system, which can be used for bio-applications without the need of ligand capping or exchange for the previously reported hydrophobic manganese(â…¡) oxide nanocrystals. In addition, a series of reduced grapheneoxide nanosheets-MnO/Fe3O4 magnetic nanoassemblies with different component ratios of Mn and Fe are also manufactured for dual-mode spin-lattice relaxation (T1) and spin-spin relaxation (T2) magnetic resonance imaging (MRI), and their magnetic and structural properties were studied by SQUID and EPR.