Quasi-Amorphous Fe₂O₃ Supraparticles For T₁-Weighted Magnetic Resonance Imaging In Vivo

The exploration of magnetic resonance contrast agents possessing clinical prospect is of great importance for both fundamental science research and biomedical applications.In this dissertation,Fe₂O₃ supraparticles?Fe₂O₃ SPs?possessing quasi-amorphous and good monodisperse are fabricated by in-situ self-assembly strategies.Then,their performances of T₁-weighted magnetic resonance imaging?MRI?and clearance mechanism in vivo are systematically studied.In detail,the dissertation mainly includes the following four parts.The first chapter is introduction of this thesis.Firstly,the synthetic methods,properties and applications of magnetic nanoparticles mainly are summarized.Secondly,we demonstrate the feature of magnetic resonance imaging,as well as the advantages and disadvantages of magnetic resonance contrast agents,respectively.Finally,due to current contrast agents lead to long-term biotoxicity problems,we propose the designs of this dissertation,namely,constructing a Fe SPs based T₁ contrast agent for magnetic resonance imaging in vivo.In the second chapter,the synthesis and properties of Fe₂O₃ SPs are mainly researched.The fabrication of Fe₂O₃ SPs by in-situ self-assembly.Firstly,systematically characterization?for example,transmission electron microscopy,X-ray photoelectron spectroscopy and X-ray absorption spectroscopy?reveals that the obtained SPs have quasi-amorphous structures and hierarchical topology,and composition of Fe₂O₃.Secondly,the formation processes Fe₂O₃ SPs are investigated based on the changes of zeta potential and particle sizes during the reaction process.Finally,relaxation properties of Fe₂O₃ SPs,as well as its influence factor?including size,pH and citrate buffer treatment?are systematically evaluated in vitro.Under optimal conditions,Fe₂O₃ SPs possess low r₂(1.91 mM^-1s^-1)and r₂/r₁ ratio?1.39?at 7 T,resulting in a high signal-to-noise ratio for T₁-weighted imaging.In the third chapter,the applications of Fe₂O₃ SPs in vivo are principally studied.The special design of quasi-amorphous structures and hierarchical topology endows the SPs unique properties in vivo MRI applications.First,Fe₂O₃ SPs exhibit good biocompatibility and very low cytotoxicity at the cellular level.Therefore,they have potential bio-application.Second,they possess remarkable imaging capacity in vivo,even the tumor sizes are as small as 5 mm³.Third,the Fe₂O₃ SPs exhibit a distinct renal clearance behavior due to their disassembled properties.Accordingly,the injected Fe₂O₃ SPs can be timely cleared from the body.Fourth,the favorable biodegradability of the prepared Fe₂O₃SPs can further relieve the concerns about the unclear biological effects,particularly on nanomaterials in general.The fourth chapter summarizes the highlight of the work and demonstrates the potential prospects.