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Magnetic–plasmonic nanoparticles (NPs) have attracted great interest in many fields because they can exhibit more physical and chemical properties than individual magnetic or plasmonic NPs. In this work, we synthesized Au- or Ag-decorated Fe3O4 nanoparticles coated with PEI (Fe3O4-PEI-M (M = Au or Ag) NPs) using a simple method. The influences of the plasmonic metal NPs' (Au or Ag) coating density on the magnetic and plasmonic properties of the Fe3O4-PEI-M (M = Au or Ag) NPs were investigated, and the density of the plasmonic metal NPs coated on the Fe3O4 NPs surfaces could be adjusted by controlling the polyethyleneimine (PEI) concentration. It showed that the Fe3O4-PEI-M (M = Au or Ag) NPs exhibited both magnetic and plasmonic properties. When the PEI concentration increased from 5 to 35 mg/mL, the coating density of the Au or Ag NPs on the Fe3O4 NPs surfaces increased, the corresponding magnetic intensity became weaker, and the plasmonic intensity was stronger. At the same time, the plasmonic resonance peak of the Fe3O4-PEI-M (M = Au or Ag) NPs was red shifted. Therefore, there was an optimal coverage of the plasmonic metal NPs on the Fe3O4 NPs surfaces to balance the magnetic and plasmonic properties when the PEI concentration was between 15 and 25 mg/mL. This result can guide the application of the Fe3O4-M (M = Au or Ag) NPs in the biomedical field. [ABSTRACT FROM AUTHOR]

Featured Application: The options for the treatment of K-Ras-driven lung tumors are currently limited. This study investigates the potential for non-thermal intervention against lung tumors using magnetic nanoparticles (MNPs) in a magnetic field. The MNPs for use in treating tumors were prepared by chemical methods. Simulations showed that the experimental platform can generate the desired magnetic field by avoiding any damaging rise in temperature and that the induced magnetic force can affect the cellular activities. Using MNPs in a magnetic field in this way can not only suppress the growth of tumor cells but also can strengthen the inhibitory effects of magnetic field stimulation on the lung tumors caused by the K-Ras mutations. K-Ras mutations result in normal cells dividing uncontrollably and becoming cancerous. The prognosis is currently poor for patients due to the lack of drugs that can effectively target these mutations. In this study, magnetic nanoparticles (MNPs) were prepared, characterized, and cooperated with a magnetic field to intervene in the growth of lung tumor cells. The rise in temperature of a stimulation coil was studied by numerical calculation. The non-thermal effects of MNPs under a magnetic force were analyzed. The cell experiments showed that the growth of A549 tumor cells slowed down. The result of a wound-healing assay also indicated that the migration of tumor cells was suppressed. Compared with magnetic stimulation without MNPs, MNPs enhanced the inhibitory effects of a magnetic field. This study suggests a new way to treat K-Ras driven lung tumors using non-thermal effects of MNPs without the side effects caused by thermal effects. [ABSTRACT FROM AUTHOR]

Featured Application: Since magnetic stimulation can activate brain tissue with optimum intensity and frequency, it demonstrates great potential for many medical applications, procedures, and treatments. For example, it makes it easier to reach a deeper region beneath the skin without causing any trauma or pain. In addition, magnetic stimulation does not leave any residues in the operated tissues. However, the magnetic fields generated by typical and conventional coils are uniform around their targets, and their magnetic stimulation performance still needs improvement. Thus, an innovative coil that has a quad coil form was proposed for transcranial magnetic stimulation, which makes it possible to shrink the irritative zone and strengthen the stimulation intensity, thus achieving higher magnetic stimulation performance. Previous research showed that pulsed functional magnetic stimulation can activate brain tissue with optimum intensity and frequency. Conventional stimulation coils are always set as a figure-8 type or Helmholtz. However, the magnetic fields generated by these coils are uniform around the target, and their magnetic stimulation performance still needs improvement. In this paper, a novel type of stimulation coil is proposed to shrink the irritative zone and strengthen the stimulation intensity. Furthermore, the electromagnetic field distribution is calculated and measured. Based on numerical simulations, the proposed coil is compared to traditional coil types. Moreover, the influential factors, such as the diameter and the intersection angle, are also analyzed. It was demonstrated that the proposed coil has a better performance in comparison with the figure-8 coil. Thus, this work suggests a new way to design stimulation coils for transcranial magnetic stimulation. [ABSTRACT FROM AUTHOR]

The focus of this paper is numerical analysis on the performance of a newly designed mega-ampere (MA) class single-stage fast linear transformer driver (FLTD) with 24 separate columns in the China Z-pinch driver CZ34. However, the internal structure and media distribution of the FLTD induction cavity is very complicated and the short rise time of the bricks' discharge current will make spatial discretization much denser, resulting in a dramatic increase in the computational complexity of a 3-D model. In this paper, the electromagnetic (EM) characteristics of the single-stage FLTD with 24-separate columns are investigated based on the time-domain finite integration theory (TD-FIT). The discharge currents of brick capacitors in the circuit model are coupled to the field model as excitations. The grid size of the key components in FLTD cavity are refined by nonuniform grids. To further reduce the number of degrees of freedom (DoFs), the surface impedance boundary condition (SIBC) is used to model good conductors. Measurements and simulation results demonstrate that TD-FIT is effective and accurate in analyzing the EM transients of FLTD. Equivalent inductance of the discharging brick will increase by ~35 nH due to the mutual flux linkage among neighboring bricks when all the 23-bricks are triggered synchronously. [ABSTRACT FROM AUTHOR]