Synthesis And Properties Of Ultrasmall Superparamagnetic MRI Contrast Agent

In recent years,because of its special properties, nano-material has been wildly applied to various aspects in biotechnology and biomedical engineering, such as magnetic separation, target drug and magnetic resonance imaging (MRI) contrast agent, et al. Currently, about one-third of MRI scans are in need of administration of a contrast agent to improve the contrast of signals. Therefore, it is of great scientific significance and diagnostic value to synthesize and study new types of MRI contrast agent.Based on the method of co-precipitation, we synthesized a kind of ultrasmall superparamagnetic iron oxide (USPIO) MRI contrast agent—nanosized iron-oxide particles surrounded by polymer. To be as USPIO MRI contrast agent, the sample must be stable, well dispersed and the diameter of the particles must be no more than 10 nm. How to get well-dispersed nanopartilces has always been one of the intense researches in the area of nanomaterial. We at last chose the polymer dextran which is biocompatible, biodegradable and hydrophilic as the coating material and get magnetic fluid in well dispersed state which can be used as MRI contrast agent. It is found that the quantity of the dextran is a major factor for the formation of stable colloid.Superparamagnetism is another indispensable property to USPIO contrast agent. We conducted magnetic measurements in two different times to the same sample. The period between the two measurements is about six months. The two results manifested both measurements have superparamagnetism and there is not much difference in the saturation magnetization. It is the coating material dextran that improved the magnetic stability. Moreover, we also studied the properties of viscidity,thermostability and surface.At last, to test the effect of our sample to be as MRI contrast agent, we conducted MRI experiments in animal liver. The results indicate that the sample we synthesized can greatly improve the signal contrast and can be a good candidate for MRI contrast agent-USPIO MRI contrast agent.