Synthesis And Application Of Metal-Doped Iron Oxide Nanoparticles Based MRI Contrast Agents

Magnetic resonance imaging(MRI)has been widely used in medical diagnosis because of its non-radiation,non-interventional and good tissue penetration.Magnetic resonance contrast agents can effectively shorten the relaxation time of water protons and improve the accuracy and specificity of MRI.Iron oxide has been widely used in the study of T2 contrast agents because of its superparamagnetism.However,for clinical diagnosis,T2 weighted imaging is not preferred,because it shows dark signals,which brings difficulties to distinguish lesions accurately.As a bright field imaging(the stronger the signal,the brighter the image),T1 weighted imaging is widely used in medical diagnosis.In addition,the current contrast agent has a single function,so it is of great significance to develop multifunctional T1 contrast agent based on iron oxide nanoparticles.In this work,we focused on the synthesis and functionalization of iron oxide nanoparticles.The magnetic and relaxation properties of iron oxide nanoparticles were studied by doping non-magnetic metal ions.Iron oxide nanoparticles were functionalized to build a multifunctional diagnosis and treatment platform.The synthesis and relaxation properties of one-dimensional iron oxide nanomaterials were also investigated.In Chapter 1,we briefly introduced the magnetic resonance imaging technology,focused on the research and development of magnetic resonance contrast agents,and put forward the research direction topic basis of this study.In Chapter 2,we synthesized calcium doped iron oxide nanoparticles in high temperature thermal decomposition conditions.A new T1 contrast agent was obtained by introducing calcium ions into iron oxide nanoparticles,and the effect of calcium doping on magnetic and relaxation properties were also studied.In Chapter 3,We synthesized a cubic iron oxide nanoparticle doped with cerium ions,constructed a multimode and multifunctional theranostics platform through surface modification.The doping of cer:ium ions significantly changed the crystal structure of the iron oxde nanoparticles,reduced the saturation magnetization,and then reduced the r2 and n2/lr1\value,making the T1 imaging effect more obvious.In addition,we successfully modified the photosensitizing molecule Ce6 on the surface to achieve the effects of photodynamic therapy and fluorescence imaging.In Chapter 4,We synthesized nanorods with different sizes and preliminarily studied their magnetic resonance imaging properties.The nanorods with different sizes have obvious differences in structure and magnetic properties.Specifically,the larger nanorods have obvious Tz contrast effect,the smaller size nanorods have obvious T1 contrast effect.In conclusion,we focused on the study of iron oxide as T1 contrast agent.By controlling the morphology and components of the nanoparticles,the effect of the morphology and components of iron oxide on magnetic properties and magnetic resonance imaging ability was studied.We have obtained non-magnetic metal ions doping iron oxide,and we found that iron oxide nanoparticles doped non-magnetic metal ions could act as T1 weighted magnetic resonance contrast agent.By functionalizing nanoparticles,iron oxide nanoparticles as a platform for diagnosis and treatment were also preliminarily explored.