Water Soluble Fe < Sub > 3 < / Sub > O < Sub > 4 < / Sub > Synthesis, Surface Modification Of Nanoparticles And Their Magnetic Resonance Imaging Studies

With the wide range of applications of MRI in clinical, it is hoped tofurther improve its detection accuracy, which need to further improvethe contrast of magnetic resonance imaging, the use of contrastagents is currently used as a way to improve contrast, many researchresults also proved its excellent. However, to make the contrast agentcan be better applied in biomedicine, the main content of this paper isdivided into two parts:（1） design a new modification of nanoparticlesto the prepared biocompatible and the specific targeting contrastagent;（2） different size Fe₃O₄nanoparticles prepared by three kinds ofthe same nature, the effects of particle size on the contrast agent inbiological applications.This paper demonstrates a surface in situ initiated epoxidering-opening polymerization strategy for synthesis of highlybiocompatible and stable, amine functionalized superaramagneticiron oxide nanoclusters （SPIONCs） for folate-receptor targetedmagnetic resonance imaging （MRI） application. The citrate stabilizedSPIONCs were prepared by a modified solvothermal reaction withbiocompatible trisodium citrate （Na3Cit） as coordination ligands. The insitu conversion of citrate hydroxyl groups to amines were realizedthrough the ring opening polymerization of epichlorohydrin and furthertreated with ammonium hydroxide. The successful amine-functionalizeof the SPIONCs was confirmed by XPS、FTIR、Zeta potential, and aminequantitative analyses. The amine-functional SPIONCs are very stable inaqueous solution as well as in cell culture medium and show lowcytoxicity to both human tumor and normal cell lines. The in vitro MRIshow significant preferential folate-receptor-mediated uptake of thefolic acid-conjugated SPIONCs （Fe₃O₄-FA） by human ovariancarcinoma cells （HeLa）. In particular, the high magnetization, good stability and effective targeting ability of the functionalized SPIONCsillustrating that these systems can be designed to be highly appropriatefor use as targted MRI contrast agents.The second part is divided into different particle sizes of the citricacid ligand-modified Fe₃O₄nanoparticles on the toxicity and cellularuptake. In this part of the experiment, we use sodium citrate as stabilizer,and first of all the of200nm Fe₃O₄nanoparticles was synthesized byHydrothermal，6nm and35nm Fe₃O₄nanoparticles were synthesizedby co-precipitation method. We characteristic by means of TEM andFTIR, the Zeta potential of the surface of Fe₃O₄nanoparticles of threedifferent particle size with similar morphology and the same chemicalproperties. And then through in vitro of MRI, cell toxicity and cellularuptake found that: the larger the particle size, the higher the rate ofmagnetic saturation, the better the imaging results; In addition, thetoxicity of the three particle size of nanoparticles on HeLa cells and PC3cells are relatively low, indicating all of them have goodbiocompatibility; but particle size has a significant impact on theamount of cellular uptake, the35-nm particles has the highest uptake,another study found that cells engulfed the200-nm particles mainlydepend on the cell uptake based.