Department of Chemistry, 207 Pleasant Street SE, University of Minnesota, Minneapolis, MN 55455, USA.
Contrast Media Mol Imaging. 2011 Jul-Aug;6(4):189-99. doi: 10.1002/cmmi.417. Epub 2010 Nov 21.
Hydrophobic magnetite nanoparticles synthesized from thermal decomposition of iron salts must be rendered hydrophilic for their application as MRI contrast agents. This process requires refunctionalizing the surface of the nanoparticles with a hydrophilic organic coating such as polyethylene glycol. Two parameters were found to influence the magnetic behavior and relaxivity of the resulting hydrophilic iron oxide nanoparticles: the functionality of the anchoring group and the protocol followed for the functionalization. Nanoparticles coated with PEGs via a catecholate-type anchoring moiety maintain the saturation magnetization and relaxivity of the hydrophobic magnetite precursor. Other anchoring functionalities, such as phosphonate, carboxylate and dopamine decrease the magnetization and relaxivity of the contrast agent. The protocol for functionalizing the nanoparticles also influences the magnetic behavior of the material. Nanoparticles refunctionalized according to a direct biphasic protocol exhibit higher relaxivity than those refunctionalized according to a two-step procedure which first involves stripping the nanoparticles. This research presents the first systematic study of both the binding moiety and the functionalization protocol on the relaxivity and magnetization of water-soluble coated iron oxide nanoparticles used as MRI contrast agents.
由铁盐热分解合成的疏水性磁铁矿纳米粒子必须被赋予亲水性，才能将其用作 MRI 造影剂。这一过程需要用亲水性有机涂层（如聚乙二醇）对纳米粒子的表面进行再功能化。有两个参数被发现会影响所得亲水氧化铁纳米粒子的磁性能和弛豫率：锚固基团的官能团和功能化所遵循的方案。通过儿茶酚型锚固基团涂覆的 PEG 纳米粒子保持了疏水性磁铁矿前体的饱和磁化强度和弛豫率。其他锚固官能团，如膦酸酯、羧酸盐和多巴胺，会降低造影剂的磁化强度和弛豫率。纳米粒子的功能化方案也会影响材料的磁性能。根据直接两相方案功能化的纳米粒子比根据先进行纳米粒子剥离的两步程序功能化的纳米粒子具有更高的弛豫率。这项研究首次对用作 MRI 造影剂的水溶性涂层氧化铁纳米粒子的结合基团和功能化方案对弛豫率和磁化率的影响进行了系统研究。
