Double Mode MRI Contrast Agent Based On Nano Self-Assembled Superlattice

Biomedical imaging technology has non-invasive advantages and has broad application prospects in clinical medicine.At present,the main biological imaging methods include X-ray,biooptical imaging,radionuclide imaging,ultrasonic imaging,nuclear magnetic resonance imaging（MRI）and so on,which are widely used in different clinical practices.Among them,MRI is widely used in the treatment and diagnosis of cancer because of its high accuracy,multi parameter analysis,multi section analysis and high safety.The MRI signals of tumor cells and normal tissue cells are sometimes difficult to distinguish,and contrast agents can target the target area to enhance the MRI signal intensity of the lesion area and further improve the accuracy of MRI.However,the first mock exam was usually done with traditional contrast media.The other endogenous conditions of human tissue will produce artifacts similar to those of contrast agents in MRI,which will affect the imaging effect of contrast agents and eventually reduce the accuracy of MRI.In order to solve this problem,this study prepared nanocomposites with cluster effect by self-assembly,coupled the contrast effect of paramagnetic and superparamagnetic contrast agents,and finally eliminated the influence of artifacts on MRI accuracy through the logical operation of"sum".The specific research contents of this study are as follows:（1）Superparamagnetic Fe₃O₄ and paramagnetic Na Gd F₄ contrast agents were synthesized by hot solvent method.The effects of sodium oleate,reaction temperature,reaction time and oleic acid concentration on the morphology,size and stability of the above nanoparticles were studied.It was found that Fe₃O₄ and Na Gd F₄ nanoparticles have good dispersion and stability in the oil phase;The size of Fe₃O₄ and Na Gd F₄nanoparticles is directly proportional to the reaction temperature and time;In addition,the addition of sodium oleate can induce the transformation of Fe₃O₄ spherical crystal into cubic crystal,and the size of Fe₃O₄ nanoparticles is inversely proportional to the concentration of oleic acid.（2）The self-assembly of Fe₃O₄ and Na Gd F₄ nanoparticles was carried out by the surfactant.The results show that Fe₃O₄ nanoparticles have better unitary self-assembly than Na Gd F₄ nanoparticles;Fe₃O₄ and Na Gd F₄ nanoparticles with different particle sizes can better realize binary assembly when the mass ratio is 10∶1;The self-assembly of Fe₃O₄-Na Gd F₄ at 16 nm and 7 nm and Fe₃O₄-Na Gd F₄ at 5 nm and 5nm were prepared respectively.（3）The MRI properties of the synthesized nano materials were explored.It was found that when DTAB was used as ligand,Fe₃O₄ and Na Gd F₄ nanoparticles showed strong T₂ and T₁ imaging functions respectively,and both nanoparticles showed better performance under smaller particle size.The synthesized binary assembly had excellent MRI dual-mode imaging function,and its T₁ and T₂ enhanced imaging effects were stronger than monodisperse Fe₃O₄ and Na Gd F₄ spherical nanoparticles respectively.