Research On Fe 3 O 4 Based Nanoparticles In MR/US Imaging And Magnetocaloric Therapy

Iron-based nanoparticles are of intense current interest for a variety of application,such as magnetic fluid,magnetic sensors,biomedical,nuclear magnetic resonance imaging,targeted drug loading,for their unique physical properties and chemical properties.These applications require iron-based nanoparticles have uniform size,good dispersion,chemical stability and so on.At present,the Fe-Fe₃O₄ nanoparticles with core-shell structure can be obtained by oxidizing a layer of Fe₃O₄ on the surface by using high temperature pyrolysis method.With the industrialization and commercialization of Fe@Fe₃O₄ core-shell magnetic nanoparticles in biomedical applications,large-scale production of reliable and stable Fe@Fe₃O₄ core-shell nanoparticles still present an important challenge.In addition,T₂ contrast agents,MR artifacts are dark signals,which frequently misinterpreted by sendogenous factors such as fat,calcification,blood clots,and artifacts are easily created to cause background image distortion.To overcome such ambiguities and accurately interpret the MRI images,T1-T₂ dual-mode contrast agents have been introduced.These dual-mode contrast agents provide complementary T1-weighted and T₂-weighted MRI images that enable self-confirmation of the signals from the contrast agents.In this paper,a series of Fe₃O₄-based multi-functional nanoparticles were designed and prepared,which were water-soluble and biocompatible by surface modification,and their structural characterization and properties were studied.The main contents of this paper are summarized as follows:Chapter 1: A general introduction to the principle of magnetic hyperthermia therapy and magnetic resonance imaging.Second,briefly describe the synthesis and applications of Fe₃O₄-based nanoparticles.Expounds the basis and research contents of this paper.Chapter 2: Fe-Fe₃O₄ nanoparticles with monodisperse,high saturation magnetization,high magnetic thermal conversion efficiency and high yield were designed and prepared.The mass production of nanoparticles was preliminarily realized.Water solubility was achieved by modified with DHCA and DMSA.The results show that the modified materials have good stability,and the ability of DHCA to protect Fe nuclei and its stability are better than that of DMSA.Based on the high saturation magnetization of Fe@Fe₃O₄ nanoparticles,we further studied the magnetic thermal conversion efficiency of Fe@Fe₃O₄ nanoparticles,.So we had demonstrated the therapy effect of Fe@Fe₃O₄-DHCA nanoparticles in vitro and in vivo.Chapter 3: On the basis of the second chapter,Fe nanoparticles were oxidized by oxidation of trimethylamine oxide（（CH3）3NO）into Yolk/Shell Fe/Fe₃O₄ and two kinds of hollow Fe₃O₄ nanoparticles with different particle size,and water solubility and biocompatibility of nanoparticles were realized by the reaction of Phospholipids and mPEG-COOH respectively.The MR and ultrasonic properties of 7 nm hollow Fe₃O₄ nanoparticles in solution and in vivo were studied.It was proved that the nanoparticles had excellent T1-T₂ dual mode imaging effect and ultrasonic effect.