Magnetic Fe_3O_4-Reduced Graphene Oxide Nanocomposites-Based Electrochemical Biosensing

An electrochemical biosensing platform was developed based on glucose oxidase(GOx)/Fe3O4-reduced graphene oxide(Fe3O4-RGO) nanosheets loaded on the magnetic glassy carbon electrode(MGCE).With the advantages of the magnetism, conductivity and biocompatibility of the Fe3O4-RGO nanosheets, the nanocomposites could be facilely adhered to the electrode surface by magnetically controllable assembling and beneficial to achieve the direct redox reactions and electrocatalytic behaviors of GOx immobilized into the nanocomposites. The biosensor exhibited good electrocatalytic activity, high sensitivity and stability. The current response is linear over glucose concentration ranging from 0.05 to 1.5 m M with a low detection limit of0.15 μM. Meanwhile, validation of the applicability of the biosensor was carried out by determining glucose in serum samples. The proposed protocol is simple, inexpensive and convenient, which shows great potential in biosensing application.

A New Tetranuclear Cubane-like Ni(Ⅱ) Complex Based on Schiff-base Ligand:Synthesis,Crystal Structure and Magnetic Properties

A new Ni（Ⅱ） cubane-like complex, namely, [Ni（L）（CH3OH）]4·（CH3OH）2, has been obtained via self-assembly of nickel（Ⅱ） and Schiff base, where the ligand L is a raceme of（R）-2-[（2-hydroxy-1-phenyl-ethylimino）-methyl]-6-methoxy-phenol. X-ray diffraction analysis reveals that the complex shows a cubane-like [Ni4O4] cluster and similar coordination environment around the metallic centers. Magnetic measurements indicate there is ferromagnetic interaction within the Ni4 cluster.

In situ assembly of magnetic nanocrystals/graphene oxide nanosheets on tumor cells enables efficient cancer therapy

Owing to the stimulus-responsive and dynamic properties,magnetism-driven assembly of building blocks to form ordered structures is always a marvelous topic.While abundant magnetic assemblies have been developed in ideal physical and chemical conditions,it remains a challenge to realize magnetic assembly in complicated biological systems.Herein,we report a kind of biomacromolecule-modified magnetic nanosheets,which are mainly composed of superparamagnetic graphene oxide(Y-Fe2O3@GO),the tumor-targeting protein transferrin(TF),and the mitochondrion-targeting peptide(MitP).Such large-size nanosheets(0.5-1μm),noted as L-Fe2O3@GO-MitP-TF,can successfully in s itu assemble on the surface of tumor cells in a size-dependent and tumor cell-specific way,leading to severe inhibition of nutrient uptake for the tumor cells.More significantly,the nanostructures could efficiently confine the tumor cells,preventing both invasion and metastasis of tumor cells both in vitro and in vivo.Moreover,the 2D assemblies could remarkably disrupt the mitochondria and induce apoptosis,remarkably eradicating tumors under near-infrared(NIR)irradiation.This study sheds light on the development of new nano-systems for efficient cancer therapy and other biomedical applications.

Construction of Multilayer Porous Scaffold Based on Magnetically Guided Assembly of Microfiber

This paper proposes a novel method of magnetically guided assembly to construct multi- layer porous scaffold for three-dimensional cell culture by apply magnetic microfibers. Microfibers are composed of biocompatible and biodegradable alginate solution with homogeneous magnetic nanopar- ticles, which are continuously spun from a microfluidic device by precise pressure control of the syringe pump. Magnetic nanoparticles enable the control of magnetic field on microfibers. Meanwhile, mag- netized device combining with a round permanent magnet are utilized to guide the distribution of spouted microfibers. The device is composed by pure iron wire arrays and wax, which stimulates pow- erful magnetic flux density and magnetic field gradients for the capture and assembly of microfibers. Thus, magnetic microfibers are spun on desired places of the magnetized device by motion control of the micromanipulation robot, and precise locations are adjusted by magnetic force couple with the assist of glass micropipette. Afterwards, microfibers are spatially organized by periodic magnetic force and crossed layer-by-layer to form micro-pore structure with both length and width of 650μm. Finally, the authors construct a multilayer microfiber-based scaffold with high porosity to provide a satisfactory environment for long-term cell culture. The experimental results demonstrate the effectiveness of the proposed method.

Stepwise assembly of heterometallic 3d–4f chain exhibiting slow magnetic relaxation

The self-assembly of polyalcohol ligand 1,1,1-tris（hydroxymethyl）ethane with Dy（NO3）3· 6H2 O and Cr3O-Bzo-t-Bu precursor in the presence of triethylamine step-by-step generated a heterometallic 3d–4f chain. Magnetic investigation of the complex indicates typical slow relaxation of the magnetization at low temperature.

Magnetic Field-Induced Solvothermal Synthesis of One-Dimensional Assemblies of Ni Co Alloy Microstructures

One-dimensional magnetic Ni Co alloy microwires with different microstructures and differently shaped building blocks including spherical particles,multilayer stacked alloy plates,and alloy flowers,have been synthesized by an external magnetic field-assisted solvothermal reaction of mixtures of cobalt(II)chloride and nickel(II)chloride in 1,2-propanediol with different NaOH concentrations.By adjusting the experimental parameters,such as precursor concentration and Ni/Co ratio,Ni Co alloy chains with uniform diameters in the range 500 nm to 1.3μm and lengths ranging from several micrometers to hundreds of micrometers can be obtained.A mechanism of formation of the one-dimensional assemblies of magnetic NiCo microparticles in a weak external magnetic fi eld is proposed.

Rotating magnetic field-controlled fabrication of magnetic hydrogel with spatially disk-like microstructures

Composite biomaterials with controllable mi- crostructures play an increasingly important role in tissue engineering and regenerative medicine. Here, we report a magnetic hydrogel composite with disk-like microstructure fabricated by assembly of iron oxide nanopartides during the gelation process in the presence of rotating magnetic field. It should be mentioned that the iron oxide nanoparticles here were synthesized identically following techniques of Fer- umoxytol that is the only inorganic nanodrug approved by FDA for clinical applications. The microstructure of nano- particles inside the hydrogel was ordered three-dimensionally due to the twist of the aligned chains of magnetic nano- particles which leads to the lowest state of systematic energy. The size of microstructure can be tuned from several micro- meters to tens of micrometers by changing the assembly parameters. With the increase of microstructure size, the magnetothermal anisotropy was also augmented. This result confirmed that the assembly-induced anisotropy can occur even for the several micron aggregates of nanopartides. The rotating magnetic field-assisted technique is cost-effective, simple and flexible for the fabrication of composite hydrogel with ordered microstructure. We believe it will be favorable for the quick, green and intelligent fabrication of some com- posite materials.

Magnetic drug delivery systems

There has been unprecedented progress in the development of biomedical nanotechnology and nanoma- terials over the past few decades, and nanoparticle-based drug delivery systems （DDSs） have great potential for clin- ical applications. Among these, magnetic drug delivery systems （MDDSs） based on magnetic nanoparticles （MNPs） are attracting increasing attention owing to their favor- able biocompatibility and excellent multifunctional loading capability. MDDSs primarily have a solid core of super paramagnetic maghemite （y-Fe^03） or magnetite （Fe304） nanoparticles ranging in size from 10 to 100nm. Their surface can be functionalized by organic and/or inorganic modification. Further conjugation with targeting ligands, drug loading, and MNP assembly can provide complex magnetic delivery systems with improved targeting efficacy and reduced toxicity. Owing to their sensitive response to external magnetic fields, MNPs and their assemblies have been developed as novel smart delivery systems. In this review, we first summarize the basic physicochemical and magnetic properties of desirable MDDSs that fulfill the requirements for specific clinical applications. Secondly, we discuss the surface modifications and functionalization issues that arise when designing elaborate MDDSs for future clinical uses. Finally, we highlight recent progress in the design and fabrication of MNPs, magnetic assemblies, and magnetic microbnbbles and liposomes as MDDSs for cancer diagnosis and therapy. Recently, researchers have focused on enhanced targeting efficacy and theranostics by applying step-by-step sequential treatment, and by magnetically mod- ulating dosing regimens, which are the current challenges for clinical applications.

Assembling and Test of a Halbach Array Magnet System for Lorentz Forece Velocimetry in Electrolytes

The paper presents a Halbach array magnet system(HAMS)for the application within a very first Lorentz force velocimetry(LFV)experiment for electrolytic flows.Here the design,assembling procedure and characterization method are presented under consideration of the strict limited weight of the system.HAMS increase the Lorentz force outcome by a factor of three compared to the currently used simple magnet systems.Furthermore the fluid profile influence on a LFV measurement on electrolytes is investigated numerically-directly on the planned test setup-and presented for the first time.Here the Lorentz forces,generated by the HAMS,decreases by 8%comparing an ideal plug-like profile at the inlet with a semi-parabolic profile arising near the outlet of the experiment.

Facile and Convenient Fabrication of Color-controlled Colloidal Magnetically Assembled Photonic Crystals

A facile, convenient and flexible method to tune the structural color of the colloidal magnetically assembled photonic crystals（CMA-PCs） was proposed. The mechanism to tune structural color could be attributed to the significant influence of the surfactant sodium dodecyl sulfate（SDS） concentration on the particle size, especially on the magnetite content of the superparamagnetic composite nanoparticles（MCNPs）. By adjusting SDS concentra- tion in miniemulsion polymerization of MCNPs, CMA-PCs with desired diffraction colors could be obtained.