Thünemann Andreas F, Schütt Dagmar, Kaufner Lutz, Pison Ulrich, Möhwald Helmuth
Federal Institute for Materials Research and Testing, Richard-Willstätter-Strasse 11, 12489 Berlin, Germany.
Langmuir. 2006 Feb 28;22(5):2351-7. doi: 10.1021/la052990d.
Superparamagnetic iron oxide particles (SPIO) of maghemite were prepared in aqueous solution and subsequently stabilized with polymers in two layer-by-layer deposition steps. The first layer around the maghemite core is formed by poly(ethylene imine) (PEI), and the second one is formed by poly(ethylene oxide)-block-poly(glutamic acid) (PEO-PGA). The hydrodynamic diameter of the particles increases stepwise from D(h) = 25 nm (parent) via 35 nm (PEI) to 46 nm (PEI plus PEO-PGA) due to stabilization. This is accompanied by a switching of their zeta-potentials from moderately positive (+28 mV) to highly positive (+50 mV) and finally slightly negative (-3 mV). By contrast, the polydispersity indexes of the particles remain constant (ca. 0.15). Mössbauer spectroscopy revealed that the iron oxide, which forms the core of the particles, is only present as Fe(III) in the form of superparamagnetic maghemite nanocrystals. The magnetic domains and the maghemite crystallites were found to be identical with a size of 12.0 +/- 0.5 nm. The coated maghemite nanoparticles were tested to be stable in water and in physiological salt solution for longer than 6 months. In contrast to novel methods for magnetic nanoparticle production, where organic solvents are necessary, the procedure proposed here can dispense with organic solvents. Magnetic resonance imaging (MRI) experiments on living rats indicate that the nanoparticles are useful as an MRI contrast agent.
在水溶液中制备了磁赤铁矿的超顺磁性氧化铁颗粒（SPIO），随后通过两层逐层沉积步骤用聚合物进行稳定化处理。磁赤铁矿核心周围的第一层由聚乙烯亚胺（PEI）形成，第二层由聚环氧乙烷-嵌段-聚谷氨酸（PEO-PGA）形成。由于稳定化作用，颗粒的流体动力学直径从D(h)=25nm（母体）逐步增加到35nm（PEI），再到46nm（PEI加PEO-PGA）。这伴随着它们的zeta电位从适度正值（+28mV）转变为高度正值（+50mV），最终变为轻微负值（-3mV）。相比之下，颗粒的多分散指数保持恒定（约0.15）。穆斯堡尔光谱表明，形成颗粒核心的氧化铁仅以超顺磁性磁赤铁矿纳米晶体的形式以Fe(III)存在。发现磁畴和磁赤铁矿微晶相同，尺寸为12.0±0.5nm。经测试，包覆的磁赤铁矿纳米颗粒在水和生理盐溶液中稳定超过6个月。与需要有机溶剂的新型磁性纳米颗粒生产方法不同，这里提出的方法可以省去有机溶剂。对活体大鼠进行的磁共振成像（MRI）实验表明，这些纳米颗粒可用作MRI造影剂。
