Research On High-Relaxivity MRI Contrast Agents Based On Cyclen

Magnetic resonance imaging (MRI) is one of medical diagnostic imaging procedure currently in use. Due to complexity of organisms, MRI cannot give enough information in some examinations. So, contrast agents (CAs) are needed to enhance the contrast between different tissues. In recent years, high-relaxivity MRI contrast agents have got more and more attentions because of the low relaxivity (r1) of CAs currently used in clinic.In this work, we have successfully synthesized amphiphilic gadolinium (â…¢) complexes as metallosurfactants and explored a new technique for preparation of MRI contrast agents through miniemulsion polymerization. Well-defined metallo-colloids in size range of 20-60 nm were obtained and characterized using a number of techniques, including SEM, TEM, DLS, ICP-AES and XPS.3T MRI measurement indicates that the prepared metallo-colloids show significant enhancement (r1= 20.4 mM-1s-1) in relaxivity due to firm interaction between amphiphilic gadolinium (III) complexes with slow tumbling polymer colloids. The colloids are also stable to dilution.In addition, we have developed a multi-modal imaging agent by incorporating fluorescent monomer (5-Acrylamidofluorescein) in miniemulsion polymerization. The results of MRI and fluorescent measurements show both high relaxivity (r1= 15.4 mM-1 s-1) and possibility of fluorescent imaging.