Zhao Zhenghuan, Sun Chengjie, Bao Jianfeng, Yang Lijiao, Wei Ruixue, Cheng Jingliang, Lin Hongyu, Gao Jinhao
State Key Laboratory of Physical Chemistry of Solid Surfaces, The MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, The Key Laboratory for Chemical Biology of Fujian Province, and iChEM, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
J Mater Chem B. 2018 Jan 21;6(3):401-413. doi: 10.1039/c7tb02954c. Epub 2017 Dec 14.
Magnetite nanoparticles, with good biocompatibility and favorable magnetic properties, have the potential to be the best candidate for non-gadolinium MRI contrast agents. However, they usually show low T contrast ability, largely because Fe(ii) ions have a short electronic relaxation time and also have a small number of unpaired electrons with inefficient proton relaxation enhancement. Herein, we report a novel strategy to increase the T contrast ability of magnetite nanoparticles, through substituting the undesirable Fe(ii) ions with Mn(ii) ions. Mn(ii) ions have a longer electronic relaxation time (10 s) and more unpaired electrons (5 unpaired electrons). We successfully construct diverse-shaped manganese ferrite nanoparticles with abundant magnetic ions, Mn(ii) and Fe(iii), exposed on the surface. These manganese ferrite nanoparticles exhibit remarkably higher longitudinal relaxivity than their parent iron oxide nanoparticles. We demonstrate that the increase in T relaxivity is attributed to the extended electronic relaxation time and the increased number of unpaired electrons on the surface of the nanoparticles by controlling surface features, particularly by adjusting the substitution degree of Mn(ii) ions and in situ coating. This study provides an insightful strategy to improve the T contrast ability of iron oxide nanoparticles, which is urgently needed for developing high-performance non-gadolinium T contrast agents for imaging and diagnosis of disease.
具有良好生物相容性和优异磁性的磁铁矿纳米颗粒，有潜力成为非钆磁共振成像（MRI）造影剂的最佳候选物。然而，它们通常表现出较低的T2造影能力，这主要是因为Fe（II）离子的电子弛豫时间短，并且未成对电子数量少，质子弛豫增强效率低。在此，我们报告了一种通过用Mn（II）离子替代不理想的Fe（II）离子来提高磁铁矿纳米颗粒T2造影能力的新策略。Mn（II）离子具有更长的电子弛豫时间（10 s）和更多的未成对电子（5个未成对电子）。我们成功构建了多种形状的锰铁氧体纳米颗粒，其表面暴露有丰富的磁性离子Mn（II）和Fe（III）。这些锰铁氧体纳米颗粒表现出比其母体氧化铁纳米颗粒显著更高的纵向弛豫率。我们证明，通过控制表面特征，特别是通过调节Mn（II）离子的取代程度和原位包覆，T2弛豫率的增加归因于纳米颗粒表面电子弛豫时间的延长和未成对电子数量的增加。本研究为提高氧化铁纳米颗粒的T2造影能力提供了一种有见地的策略，这是开发用于疾病成像和诊断的高性能非钆T2*造影剂迫切需要的。
