Department of Chemistry, Shanghai Normal University, No.100 Guilin Road, Shanghai 200234, People's Republic of China.
Nanotechnology. 2011 Feb 25;22(8):085707. doi: 10.1088/0957-4484/22/8/085707. Epub 2011 Jan 18.
MnFe(2)O(4) nanocrystals (NCs) coated with three different surfactants (oleic acid, oleylamine or 1,2-hexadecanediol) and their mixtures, with sizes in range 6-12 nm, were synthesized by high-temperature decomposition of organometallic precursors. The effects of morphology and surface chemistry of MnFe(2)O(4) NCs on the magnetic properties were systematically investigated by comparing their saturation magnetization values and their capability to improve the negative contrast for magnetic resonance imaging (MRI) after converting the hydrophobic NCs to hydrophilic ones by a ligand exchange protocol. An important finding is that the magnetization values and proton relaxivity rates of MnFe(2)O(4) NCs are strongly dependent on the size and surface state of the particles that covalently bonded with different hydrophobic ligands before ligand exchange. In particular, monodisperse cubic MnFe(2)O(4) NCs could be obtained when oleylamine and 1,2-hexadecanediol were used as mixed stabilizers, and showed excellent morphology and magnetic properties. Furthermore, the low cytotoxicity and good cell uptake MR imaging of the dopamine capped MnFe(2)O(4) NCs make them promising candidates for use as bio-imaging probes.
用三种不同的表面活性剂（油酸、油胺或 1,2-十六烷二醇）和它们的混合物包覆的 MnFe(2)O(4)纳米晶体（NCs），尺寸在 6-12nm 范围内，通过高温分解有机金属前驱体制备。通过比较饱和磁化强度值以及通过配体交换将疏水性 NCs 转化为亲水性 NCs 后改善磁共振成像（MRI）的负对比能力，系统研究了 MnFe(2)O(4)NCs 的形态和表面化学对磁性的影响。一个重要的发现是，MnFe(2)O(4)NCs 的磁化值和质子弛豫率强烈依赖于颗粒的大小和表面状态，这些颗粒在配体交换之前与不同的疏水性配体共价键合。特别是，当油胺和 1,2-十六烷二醇用作混合稳定剂时，可以获得单分散立方 MnFe(2)O(4)NCs，并且表现出优异的形态和磁性。此外，多巴胺封端的 MnFe(2)O(4)NCs 的低细胞毒性和良好的细胞摄取 MRI 使得它们有望用作生物成像探针。
