Hou Yanglong

Chemical synthesis of magnetic nanocrystals: Recent progress

Colloidal chemical synthesis of various types of magnetic nanocrystals is discussed with regard to recent discoveries. We first outline the chemical preparation of single-component magnetic nanocrystals with controlled size, shape, and uniformity based on several solution-phase methods, especially thermal decomposition and/or reduction method. Then we discuss the synthetic strategies of multi-component nanocrystals incorporating at least one magnetic component by manipulating heterogeneous nucleation and growth process. Toward the end, approaches for preparing hollow/porous magnetic nanocrystals are highlighted. We believe that the summarized chemical synthesis will pave the way for the future development of extraordinary magnetic nanocrystals.

Magnetic iron oxide nanoparticles: Synthesis and surface coating techniques for biomedical applications

Iron oxide nanoparticles are the most popular magnetic nanoparticles used in biomedical applications due to their low cost, low toxicity, and unique magnetic property. Magnetic iron oxide nanoparticles, including magnetite (Fe3O4) and maghemite (?-Fe2O3), usually exhibit a superparamagnetic property as their size goes smaller than 20 nm, which are often denoted as superparamagnetic iron oxide nanoparticles (SPIONs) and utilized for drug delivery, diagnosis, therapy, and etc. This review article gives a brief introduction on magnetic iron oxide nanoparticles in terms of their fundamentals of magnetism, magnetic resonance imaging (MRI), and drug delivery, as well as the synthesis approaches, surface coating, and application examples from recent key literatures. Because the quality and surface chemistry play important roles in biomedical applications, our review focuses on the synthesis approaches and surface modifications of iron oxide nanoparticles. We aim to provide a detailed introduction to readers who are new to this field, helping them to choose suitable synthesis methods and to optimize the surface chemistry of iron oxide nanoparticles for their interests.

Surface modification of magnetic nanoparticles in biomedicine

Progress in surface modification of magnetic nanoparticles (MNPs) is summarized with regard to organic molecules, macromolecules and inorganic materials. Many researchers are now devoted to synthesizing new types of multi-functional MNPs, which show great application potential in both diagnosis and treatment of disease. By employing an ever-greater variety of surface modification techniques, MNPs can satisfy more and more of the demands of medical practice in areas like magnetic resonance imaging (MRI), fluorescent marking, cell targeting, and drug delivery.

Magnetic nanoparticle-based cancer therapy

Nanoparticles (NPs) with easily modified surfaces have been playing an important role in biomedicine. As cancer is one of the major causes of death, tremendous efforts have been devoted to advance the methods of cancer diagnosis and therapy. Recently, magnetic nanoparticles (MNPs) that are responsive to a magnetic field have shown great promise in cancer therapy. Compared with traditional cancer therapy, magnetic field triggered therapeutic approaches can treat cancer in an unconventional but more effective and safer way. In this review, we will discuss the recent progress in cancer therapies based on MNPs, mainly including magnetic hyperthermia, magnetic specific targeting, magnetically controlled drug delivery, magnetofection, and magnetic switches for controlling cell fate. Some recently developed strategies such as magnetic resonance imaging (MRI) monitoring cancer therapy and magnetic tissue engineering are also addressed.

Nanomagnetism: Principles, nanostructures, and biomedical applications

Nanomagnetism is the origin of many unique properties in magnetic nanomaterials that can be used as building blocks in information technology, spintronics, and biomedicine. Progresses in nanomagnetic principles, distinct magnetic nanostructures, and the biomedical applications of nanomagnetism are summarized.

Tuning crystal structure and magnetic property of dispersible FePt intermetallic nanoparticles

Dispersible FePt intermetallic nanoparticles (NPs) with tunable composition were synthesized by thermal annealing of MgO coated Al-FePt (or Al-FePt-Fe3O4) NPs followed by an acid treatment to remove MgO. High-temperature annealing facilitates the conversion of FePt from disordered alloy to ordered intermetallics. Under the protection of MgO, the diffusion of Fe and Pt atoms was limited, making it possible for the atom reconstruction in the lattice to give discrete FePt intermetallic NPs after a facile acid etching process. FePt intermetallic NPs formed face-centered cubic and face-centered tetragonal structures with their magnetic properties tuned by composition. The saturation magnetization was adjusted from 8 to 52 emu g−1 by increasing the Fe concentration, while the coercivity reached a maximum of 33 kOe when Fe concentration was 44%. After surface modifications by hydrophilic or hydrophobic molecules containing thiol groups, FePt intermetallic NPs could be dissolved into water or hydrocarbon solvents. The hydrophilic L10-FePt intermetallic NPs were applied as contrast agents for magnetic resonance imaging, showing a high transverse relaxivity of 328.6 mmol−1 L s−1, which indicated the great potential of FePt intermetallic NPs as molecular probes for cancer diagnosis.摘要具有可调组分的单分散FePt金属间化合物纳米颗粒由MgO包覆的Al-FePt(或者Al-FePt-Fe3O4)经过热退火, 再通过酸处理除去MgO制备得到. 高温退火有助于FePt从无序合金转变为有序金属间化合物. 在MgO的保护下, Fe和Pt的扩散受到限制, 因而晶格中的Fe、 Pt原子能够重构形成FePt金属间化合物, 再通过简单的酸腐蚀可得到分散的纳米颗粒. FePt金属间化合物纳米颗粒形成面心立方和面心四方结构, 通过组分调节可以改变其磁性能. 随着铁含量的增加, 其饱和磁化强度从8 emu g−1提高到52 emu g−1, 在铁含量为44%时, 矫顽力达到最大值33 kOe. 利用含巯基分子对纳米颗粒表面进行亲水或疏水性改性, FePt金属间化合物纳米颗粒可以溶于水和烃类溶剂. 亲水的L10-FePt金属间化合物纳米颗粒可作为磁共振成像造影剂, 表现出高的横向弛豫率(328.6 mmol−1 L s−1), 这表明FePt金属间化合物纳米颗粒有望用于肿瘤诊断的分子探针.