Authors: Hai-Ming Fan,*  Malini Olivo, Borys Shuter, Jia-Bao Yi, Ramaswamy Bhuvaneswari, Hui-Ru Tan, Gui-Chuan Xing,  Cheng-Teng Ng, Lei Liu, Sasidharan S. Lucky, Boon-Huat Bay, and Jun Ding

期刊： J. Am. Chem. Soc. 2010, 132, 14803–14811

摘要: In the present study, quantum dot (QD) capped magnetite nanorings (NRs) with a high luminescence and magnetic vortex core have been successfully developed as a new class of magneticfluorescent  nanoprobe. Through electrostatic interaction, cationic polyethylenimine (PEI) capped QD have been firmly grafted into negatively charged magnetite NRs modified with citric acid on the surface. The obtained biocompatible multicolor QD capped magnetite NRs exhibit a much stronger magnetic resonance (MR) T2* effect where the r2* relaxivity and r2*/r1 ratio are 4 times and 110 times respectively larger than those
of a commercial superparamagnetic iron oxide. The multiphoton fluorescence imaging and cell uptake of
QD capped magnetite NRs are also demonstrated using MGH bladder cancer cells. In particular, these
QD capped magnetite NRs can escape from endosomes and be released into the cytoplasm. The obtained
results from these exploratory experiments suggest that the cell-penetrating QD capped magnetite NRs
could be an excellent dual-modality nanoprobe for intracellular imaging and therapeutic applications. This
work has shown great potential of the magnetic vortex core based multifunctional nanoparticle as a high
performance nanoprobe for biomedical applications.

简评： 氧化铁纳米环的合成和制备已经在前期报道了很多。其特殊的形貌结构导致了稳定涡旋磁态(vortex state)的存在，这个vortex state 在外场的作用下可以磁化转成onion state。涡旋磁态的存在和 两个态之间的transition在过去5年已经在包括Science, PRL 等一系列顶级杂志中发表的论文里进行了详细的讨论。 然后其应用领域尚未有所突破，近期在nature physics上有论文报道关于利用vortex spin有效杀死癌症细胞的例子。本文利用其涡旋磁态时，颗粒之间弱的磁相互作用形成了较稳定的水相分散体，并嫁接了荧光量子点赋予其光学性能。这个复合的纳米环定义为，QD-FVIOs. 其中FVIO is ferrimagnetic/ferromagnetic vortex-state iron oxides.在磁共振成像的表征上发现，相对于超顺磁的氧化铁，涡旋磁态氧化铁表现了非常高的T2*效应。细胞荧光成像实验和MRI成像实验结果表明，这种基于vortex state 的纳米磁环结构在生物医学和细胞成像(cell imaging)上有着很大的用途。详情请参考论文。