Super stable water-based magnetic fluid as a dual-mode contrast agent

Abstract

Abstract Early diagnosis of cancer has become one of the effective ways to prevent and treat cancer. At present, magnetic resonance imaging (MRI) diagnosis based on nanosized iron oxide with no toxicity and excellent biocompatibility has attracted much attention. But the poor stability of magnetic fluid (MF) is becoming more and more prominent. In view of the poor stability of MF, the dodecanethiol-poly(methacrylic acid) (DDT-PMAA) as an outer shell was prepared for the MFs (Fe3O4@DDT-PMAA MF) to improve the stability. We also compared the amount of reactants, the ratio of reactants, and the reaction temperature, and finally screened out the best reaction conditions, so as to get more stable products. The stability of the system was studied by visual observation, stability index (I), and magnetic weight change. The results demonstrated that Fe3O4@DDT-PMAA can be stable for more than 60 days. The T 1 mapping image showed that the longitudinal relaxivity (r 1) value was 6.9 mM−1 s−1 (1.5 T, room temperature), which was higher than the commercial contrast agent SHU-555 (r 1 = 2.9 mM−1 s−1), but the transverse relaxivity (r 2) value accounted for 64.48% of the commercial contrast agent Feridex (r 2 = 67.8 mM−1 s−1, 1.5 T, room temperature) because the outermost layer was encapsulated by a polymer. In addition, the imaging effect was more vivid and there was almost no background interference of T 1- and T 2-weighted images in vivo, which indicated that the Fe3O4@DDT-PMAA MF exhibited excellent potential in MRI applications.