[15a-P8-1~31] 12.1 作製・構造制御

▲ [15a-P8-28] Fabrication of Magnetic Nanoparticles as Potential Contrast Agent for Magnetic Resonance Imaging (MRI)

〇(M2)Pornrungroj Chanon¹、Dahanayake Vidumin¹、Hickling William¹、Keuran Edward¹、Stoll Sarah¹ (1.Georgetown Univ.)

キーワード：contrast agents, magnetic cluster, miniemulsion

MRI technique is a well-known noninvasive imaging technique based on Magnetic Resonance. However, it is difficult to apply this technique for tumor imaging. This is because the tumor physical property is mostly identical with the surrounding tissue, therefore it shows the same contrast during MR Imaging. Currently, the gadolinium (Gd) based contrast agent such as Magnevist® is injected into the patience prior the imaging to effectively change the magnetic property (T1 brightening effect) of the tumor cell. Although Gd is effective, it is dangerous for our body as humans do not have a metabolic pathway for Gd. The use of Gd based agents has also been linked to nephrogenic systemic fibrosis (NSF) in patients. It is important that we develop a new generation of benign contrast agents that are competitive with commercial Gd based contrast agents. As previously reported, Mn8Fe4VBA magnetic cluster encapsulated in polymer nanoparticles (NPs) represents a potential candidate as contrast agent. The NPs were successfully uptaken by PC3 prostate cancer cells and showed a good contrast. Despite no metal leaching observed and high cell viability, the system is still less effective than Gd based system. In this work, a very promising magnetic cluster Mn3bpy² has been explored as a next generation contrast agent. The Mn₃bpy polyacrylamide nanoparticles (PAm Mn₃bpy NPs) were successfully fabricated using the inverse-miniemulsion technique. The size of PAm Mn₃bpy NPs in cyclohexane was determined by utilizing Dynamic light scattering. The obtained result 130.9 nm has been confirmed by SEM and TEM. When dried and re-suspended in water, the swelling of the PAm Mn₃bpy NPs in aqueous solution was observed as the average size increased to 221.2 nm in diameter, whereas the suspension remained highly monodispersed. The swelling of NPs is rather typical for hydrophilic polymer NPs in salt-free solution. In addition, the TEM also indicated that the metal dispersion was highly homogeneous compare with inhomogeneous iron oxide NPs. We have conducted the metal leaching experiments, and our results indicated that unreacted Mn leaching from PAm Mn₃bpy NPs became insignificant after 3-4 washes. As polyacrylamide is hydrophilic, the dried solid can be easily re-suspended in solution without the addition of surfactant. This is particularly advantageous for a contrast agent, because it allows storage of the agent over a long period of time. Moreover, the ability to modify the surface of this NPs could potentially be useful for targeted drug delivery. Our finding will positively contribute to the development of next generation Mn(II) based contrast agents.