Magnetic-plasmonic dual modulated FePt-Au ternary heterostructured nanorods as a promising nano-bioprobe

Advances in FePt-involved nano-system design and application for bioeffect and biosafety

The rapid development and wide application of nanomaterial-involved theranostic agents have drawn surging attention for improving the living standard of humankind and healthcare conditions. In this review, recent developments in the design, synthesis, biocompatibility evaluation and potential nanomedicine applications of FePt-involved nano-systems are summarized, especially for cancer theranostic and biological molecule detection. The in vivo multi-model imaging capability is discussed in detail, including magnetic resonance imaging and computed tomography. Furthermore, we highlight the significant achievements of various FePt-involved nanotherapeutics for cancer treatment, such as drug delivery, chemodynamic therapy, photodynamic therapy, radiotherapy and immunotherapy. In addition, a series of FePt-involved nanocomposites are also applied for biological molecule detection, such as H₂O₂, glucose and naked-eye detection of cancer cells. Ultimately, we also summarize the challenges and prospects of FePt-involved nano-systems in nanocatalytic medicine. This review is expected to give a general pattern for the development of FePt-involved nano-systems in the field of nanocatalytic medicine and analytical determination.

Magneto-Ionics in Single-Layer Transition Metal Nitrides

Magneto-ionics allows for tunable control of magnetism by voltage-driven transport of ions, traditionally oxygen or lithium and, more recently, hydrogen, fluorine, or nitrogen. Here, magneto-ionic effects in single-layer iron nitride films are demonstrated, and their performance is evaluated at room temperature and compared with previously studied cobalt nitrides. Iron nitrides require increased activation energy and, under high bias, exhibit more modest rates of magneto-ionic motion than cobalt nitrides. Ab initio calculations reveal that, based on the atomic bonding strength, the critical field required to induce nitrogen-ion motion is higher in iron nitrides (≈6.6 V nm^-1) than in cobalt nitrides (≈5.3 V nm^-1). Nonetheless, under large bias (i.e., well above the magneto-ionic onset and, thus, when magneto-ionics is fully activated), iron nitride films exhibit enhanced coercivity and larger generated saturation magnetization, surpassing many of the features of cobalt nitrides. The microstructural effects responsible for these enhanced magneto-ionic effects are discussed. These results open up the potential integration of magneto-ionics in existing nitride semiconductor materials in view of advanced memory system architectures.

Magnetically controllable metasurface and its application

The dynamic control of the metasurface opens up a vital technological approach for the development of multifunctional integrated optical devices. The magnetic field manipulation has the advantages of sub-nanosecond ultra-fast response, non-contact, and continuous adjustment. Thus, the magnetically controllable metasurface has attracted significant attention in recent years. This study introduces the basic principles of the Faraday and Kerr effect of magneto-optical (MO) materials. It classifies the typical MO materials according to their properties. It also summarizes the physical mechanism of different MO metasurfaces that combine the MO effect with plasmonic or dielectric resonance. Besides, their applications in the nonreciprocal device and MO sensing are demonstrated. The future perspectives and challenges of the research on MO metasurfaces are discussed.

Influence of Cu on the Improvement of Magnetic Properties and Structure of L10 FePt Nanoparticles

L1₀ ordered FePt and FePtCu nanoparticles (NPs) with a good dispersion were successfully fabricated by a simple, green, one-step solid-phase reduction method. Fe (acac)₃, Pt (acac)₂, and CuO as the precursors were dispersed in NaCl and annealed at different temperatures with an H₂-containing atmosphere. As the annealing temperature increased, the chemical order parameter (S), average particle size (D), coercivity (H_c), and saturation magnetization (M_s) of FePt and FePtCu NPs increased and the size distribution range of the particles became wider. The ordered degree, D, H_c, and M_s of FePt NPs were greatly improved by adding 5% Cu. The highest S, D, H_c, and M_s were obtained when FePtCu NPs annealed at 750 °C, which were 0.91, 4.87 nm, 12,200 Oe, and 23.38 emu/g, respectively. The structure and magnetic properties of FePt and FePtCu NPs at different annealing temperatures were investigated and the formation mechanism of FePt and FePtCu NPs were discussed in detail.

X-ray Free Electron Laser-Induced Synthesis of ε-Iron Nitride at High Pressures

The ultrafast synthesis of ε-Fe₃N_1+x in a diamond-anvil cell (DAC) from Fe and N₂ under pressure was observed using serial exposures of an X-ray free electron laser (XFEL). When the sample at 5 GPa was irradiated by a pulse train separated by 443 ns, the estimated sample temperature at the delay time was above 1400 K, confirmed by in situ transformation of α- to γ-iron. Ultimately, the Fe and N₂ reacted uniformly throughout the beam path to form Fe₃N_1.33, as deduced from its established equation of state (EOS). We thus demonstrate that the activation energy provided by intense X-ray exposures in an XFEL can be coupled with the source time structure to enable exploration of the time-dependence of reactions under high-pressure conditions.

ZnO Nanolower-Based NanoPCR as an Efficient Diagnostic Tool for Quick Diagnosis of Canine Vector-Borne Pathogens

Polymerase chain reaction (PCR) is a unique technique in molecular biology and biotechnology for amplifying target DNA strands, and is also considered as a gold standard for the diagnosis of many canine diseases as well as many other infectious diseases. However, PCR still faces many challenges and issues related to its sensitivity, specificity, efficiency, and turnaround time. To address these issues, we described the use of unique ZnO nanoflowers in PCR reaction and an efficient ZnO nanoflower-based PCR (nanoPCR) for the molecular diagnosis of canine vector-borne diseases (CVBDs). A total of 1 mM of an aqueous solution of ZnO nanoflowers incorporated in PCR showed a significant enhancement of the PCR assay with respect to its sensitivity and specificity for the diagnosis of two important CVBDs, Babesia canis vogeli and Hepatozoon canis. Interestingly, it drastically reduced the turnaround time of the PCR assay without compromising the yield of the amplified DNA, which can be of benefit for veterinary practitioners for the improved management of diseases. This can be attributed to the favorable adsorption of ZnO nanoflowers to the DNA and thermal conductivity of ZnO nanoflowers. The unique ZnO nanoflower-assisted nanoPCR greatly improved the yield, purity, and quality of the amplified products, but the mechanism behind these properties and the effects and changes due to the different concentrations of ZnO nanoflowers in the PCR system needs to be further studied.

Multisegmented Metallic Nanorods: Sub-10 nm Growth, Nanoscale Manipulation, and Subwavelength Imaging

Multisegmented metallic nanorods (MS-M-NRs) have attracted increasing attention thanks to their integrated structures and complex functions. The integration of nanoscale segments in 1D enables maximum exposure of each segment and enhanced interaction between adjacent segments. Such structural integration will induce functional complexity in the nanorods, leading to superior properties for the individual components. Herein, recent progress on the development of MS-M-NRs is reviewed. Their precise fabrication, nanoscale manipulation, and subwavelength imaging, as well as simultaneous manipulation and imaging are discussed, respectively. Specifically, precise fabrication of MS-M-NRs focuses on porous anodic alumina (PAA) templated electrodeposition, which enables sub-10 nm growth of the segments and their interfaces/fronts. Nanoscale manipulation of MS-M-NRs introduces the fundamental methods that are employed for delicate movement control on the nanorods through internal or external stimulations. Subwavelength imaging of MS-M-NRs highlights the achievements on identification and location of constituent nanoscale segments/gaps based on their differences and interactions. Simultaneous manipulation and imaging of MS-M-NRs addresses the significance and potential applications of the nanorods with magnetic-plasmonic dual modulation. The development of MS-M-NRs will greatly contribute to materials science and nanoscience/nanotechnology.

Robust Assembly of Colloidal Nanoparticles for Controlled-Reflectance Surface Construction

Controlled placement of nanoscale particles with nanometer precision on substrates/surfaces is highly desired toward functional nanodevices. Herein, we report the robust assembly of colloidal nanoparticles onto nanostructured aluminum surfaces. The surfaces are configured by porous anodic alumina (PAA) membranes on top of textured aluminum substrates. Capillary force and geometry confinement enable rapid and precise transfer of colloidal nanoparticles from solutions into PAA templates. Such top-down control of bottom-up assembly demonstrates large-area (>1 × 1 cm²) integration of nanoscale particles with exceedingly high yield (>95%) and exceptionally high density (>10¹⁰ particles/cm²). The plasmonic coupling between gold nanoparticles and aluminum surfaces, as well as between adjacent nanoparticles, is responsible for the unique reflectance from the assembled surfaces. The reflectance minimum (resonant absorption) can be readily shifted from visible to near-infrared by simple structural variation. The apparent surface colors are thus broadly manipulated. Our work offers a straightforward platform toward construction of surfaces with controlled reflectance.

Biomechanical Characterization at the Cell Scale: Present and Prospects

The rapidly growing field of mechanobiology demands for robust and reproducible characterization of cell mechanical properties. Recent achievements in understanding the mechanical regulation of cell fate largely rely on technological platforms capable of probing the mechanical response of living cells and their physico–chemical interaction with the microenvironment. Besides the established family of atomic force microscopy (AFM) based methods, other approaches include optical, magnetic, and acoustic tweezers, as well as sensing substrates that take advantage of biomaterials chemistry and microfabrication techniques. In this review, we introduce the available methods with an emphasis on the most recent advances, and we discuss the challenges associated with their implementation.

Multi-block magnetic nanorods for controlled drug release modulated by Fourier transform surface plasmon resonance

Stimuli-responsive tunable drug release using nanocarriers is an important subject in smart drug delivery systems. Specifically, magnetic-responsive nanocarriers provide a great opportunity for remote control as well as on-demand command. To effectively utilize magnetic-responsive nanocarriers in vivo and in vitro, drug release should not only be controlled in an efficient way, but also monitored in situ. To satisfy those prerequisites, a template-assisted electrochemical deposition method can be a great option for the synthesis of designer materials that are targeted for specific purposes. Here, we synthesized plasmonic-magnetic nanocarriers by template-assisted electrochemical deposition and covered their surface with a silica shell for drug loading. By appropriately designing the blocks, we synthesized nanocarriers that were plasmonically active and magnetically active with spaces for drug payload. These nanocarriers could be modulated under an external magnetic field and their rotation (or agitation) could be monitored by Fourier transform conversion. Using our nanocarriers, we systematically investigated the tunable release of the anticancer drug doxorubicin as a function of the external magnetic field. Additionally, by applying this modulation system to an in vitro system using HeLa cells we were able to not only monitor the modulation systems but also tailor the drug release in a controlled manner. We expect that our approach will contribute to understanding of nanocarriers in a simulative manner in vitro.

Linear self-assembly and grafting of gold nanorods into arrayed micrometer-long nanowires on a silicon wafer via a combined top-down/bottom-up approach

Macroscopically long wire-like arrangements of gold nanoparticles were obtained by controlled evaporation and partial coalescence of an aqueous colloidal solution of capped CTAB-Au nanorods onto a functionalised 3-mercaptopropyl trimethoxysilane (MPTMS) silicon substrate, using a removable, silicon wafer with a hydrophobic surface that serves as a "handrail" for the initial nanorods' linear self-assembly. The wire-like structures display a quasi-continuous pattern by thermal annealing of the gold nanorods when the solvent (i.e. water) is evaporated at temperatures rising from 20°C to 140°C. Formation of both single and self-replicating parallel 1D-superstructures consisting of two or even three wires is observed and explained under such conditions.

Flower-like ZnO nanostructure assisted loop-mediated isothermal amplification assay for detection of Japanese encephalitis virus

In this study, we described a novel and effective flower-like ZnO nanostructure assisted Reverse Transcription Loop-Mediated Isothermal Amplification (RT-LAMP) method to detect Japanese Encephalitis Virus (JEV). The effects of different concentrations of ZnO nanoflower on the RT-LAMP reaction were investigated. With the increase of concentration of ZnO nanoflower, RT-LAMP reaction obtained optimization, until the concentration exceeded 1.5nM, RT-LAMP reaction was inhibited. Made 1nM as optimum concentration of ZnO nanoflower, we found that optimum RT-LAMP reaction temperature and time were 60°C and 30min, respectively. The optimization might be connected with good adsorption to DNA and thermal conductivity of ZnO nanoflower, but mechanism of the RT-LAMP reaction affected by ZnO nanoflower needs to be explored further.

Assembly-Induced Thermogenesis of Gold Nanoparticles in the Presence of Alternating Magnetic Field for Controllable Drug Release of Hydrogel

Films of gold nanoparticles are easily fabricated by layer-by-layer assembly. With increasing number of layers a transition of the electric property from insulating to conducting can be achieved. This conductivity leads to controllable thermogenesis of the film, which can be employed for drug release of loaded hydrogels.

Bio-Nano-Magnetic Materials for Localized Mechanochemical Stimulation of Cell Growth and Death

Magnetic nanoparticles are promising new tools for therapeutic applications, such as magnetic nanoparticle hyperthermia therapy and targeted drug delivery. Recent in vitro studies have demonstrated that a force application with magnetic tweezers can also affect cell fate, suggesting a therapeutic potential for magnetically modulated mechanical stimulation. The magnetic properties of nanoparticles that induce physical responses and the subtle responses that result from mechanically induced membrane damage and/or intracellular signaling are evaluated. Magnetic particles with various physical, geometric, and magnetic properties and specific functionalization can now be used to apply mechanical force to specific regions of cells, which permit the modulation of cellular behavior through the use of spatially and time controlled magnetic fields. On one hand, mechanochemical stimulation has been used to direct the outgrowth on neuronal growth cones, indicating a therapeutic potential for neural repair. On the other hand, it has been used to kill cancer cells that preferentially express specific receptors. Advances made in the synthesis and characterization of magnetic nanomaterials and a better understanding of cellular mechanotransduction mechanisms may support the translation of mechanochemical stimulation into the clinic as an emerging therapeutic approach.

High magnetic field-induced synthesis of one-dimensional FePt nanomaterials

High magnetic field can facilitate one-dimensional anisotropic growth of FePt nanomaterials through inducing orientation-attachment.

Multifunctional FePt–Au heterodimers: promising nanotheranostic agents for dual-modality MR/CT imaging diagnosis and in situ cancer therapy

We report the synthesis of multifunctional FePt–Au hybrid nanoparticles via a simple hydrothermal approach and their potential application in cancer dual-modality MR/CT imaging diagnosis and simultaneous in situ therapy.

Mechanochemical stimulation of MCF7 cells with rod-shaped Fe-Au Janus particles induces cell death through paradoxical hyperactivation of ERK

Multifunctional nanoparticles that actively target-specific tissues are studied for cancer diagnosis and treatment. Magnetically and optically active particles are of particular interest because they enable multiple imaging modalities and physically modulated therapies, such as magnetic hyperthermia. Fe-Au nanorods are synthesized that have a long iron segment, coated with polyethylene glycol, and a short gold tip functionalized with heregulin (HRG), a known ligand of ErbB family of receptors. HRG-nanorods preferentially target MCF7 cells relative to MDA-MB-231 cells, as demonstrated in a novel microfluidics device. Targeting rates of these classical breast cancer cells correlate with their differential expression of ErbB2/3 receptors. HRG-nanorod binding stimulates the extracellular signal-regulated kinase 1/2 (ERK) phosphorylation in MCF7 cells. The increase in ERK phosphorylation is linked to "active zones," dynamic regions in the cell periphery, which exhibit higher rates of particle binding than the rest of the cell. Periodically stretching cells using magnetic tweezers further activates ERK, which leads to cell death in cells co-treated with B-Raf inhibitors, through ERK hyperactivation. Although to a lesser extent, cell death is also achieved through magnetic hyperthermia. These results demonstrate nanoscale targeting and localized mechanochemical treatment of specific cancer cell lines based on their receptor expression using multifunctional nanoparticles.

Plasmonic enhancement of dye sensitized solar cells via a tailored size-distribution of chemically functionalized gold nanoparticles

A substantial and stable increase of the current density J_sc of ruthenium (Ru) dye sensitized solar cells (DSC) of up to 16.18% and of the power efficiency of up to 25.5% is demonstrated in this article via plasmonic enhancement. The key aspect of this work is the use of a tailored bimodal size distribution of functionalized gold nanoparticles (AuNPs) that have been chemically immobilized onto the mesoporous titanium dioxide (TiO₂) layer via short, stable dithiodibutyric acid linkers. The size distribution of the AuNPs is a result of theoretical calculations that aimed at the perfection of the absorption characteristics of the complete solar cell system over a wide range of wavelengths. The functionalization of the AuNPs serves to bind them at a close but defined distance to TiO₂-particles and additionally to chemically protect them against potential corrosion by the electrolyte. Simulations of near field (enhanced absorption) and far field (scattering) contributions have been used to tailor a complex AuNPs bimodal size distribution that had subsequently demonstrated experimentally a close to optimum improvement of the absorbance over a wide wavelength range (500–675 nm) and therefore an impressive DSC efficiency enhancement. Finally, the modified DSCs are exhibiting pronounced longevity and stable performance as confirmed via long time measurements. In summary, the presented systems show increased performance compared to non plasmonic enhanced cells with otherwise identical composition, and are demonstrating a previously unpublished longevity for iodide electrolyte/AuNPs combinations.

Controlled synthesis of organic nanophotonic materials with specific structures and compositions

Organic nanomaterials have drawn great interest for their potential applications in high-speed miniaturized photonic integration due to their high photoluminescence quantum efficiency, structural processability, ultrafast photoresponse, and excellent property engineering. Based on the rational design on morphological and componential levels, a series of organic nanomaterials have been controllably synthesized in recent years, and their excitonic/photonic behaviors has been fine-tuned to steer the light flow for specific optical applications. This review presents a comprehensive summary of recent breakthroughs in the controlled synthesis of organic nanomaterials with specific structures and compositions, whose tunable photonic properties would provide a novel platform for multifunctional applications. First, we give a general overview of the tailored construction of novel nanostructures with various photonic properties. Then, we summarize the design and controllable synthesis of composite materials for the modulation of their functionalities. Subsequently, special emphasis is put on the fabrication of complex nanostructures towards wide applications in isolated photonic devices. We conclude with our personal viewpoints on the development directions in the novel design and controllable construction of organic nanomaterials for future applications in highly integrated photonic devices and chips.

Magneto-plasmonic Au-Fe alloy nanoparticles designed for multimodal SERS-MRI-CT imaging

Diagnostic approaches based on multimodal imaging are needed for accurate selection of the therapeutic regimens in several diseases, although the dose of administered contrast drugs must be reduced to minimize side effects. Therefore, large efforts are deployed in the development of multimodal contrast agents (MCAs) that permit the complementary visualization of the same diseased area with different sensitivity and different spatial resolution by applying multiple diagnostic techniques. Ideally, MCAs should also allow imaging of diseased tissues with high spatial resolution during surgical interventions. Here a new system based on multifunctional Au-Fe alloy nanoparticles designed to satisfy the main requirements of an ideal MCA is reported and their biocompatibility and imaging capability are described. The MCAs show easy and versatile surface conjugation with thiolated molecules, magnetic resonance imaging (MRI) and computed X-ray tomography (CT) signals for anatomical and physiological information (i.e., diagnostic and prognostic imaging), large Raman signals amplified by surface enhanced Raman scattering (SERS) for high sensitivity and high resolution intrasurgical imaging, biocompatibility, exploitability for in vivo use and capability of selective accumulation in tumors by enhanced permeability and retention effect. Taken together, these results show that Au-Fe nanoalloys are excellent candidates as multimodal MRI-CT-SERS imaging agents.

Drug loaded multilayered gold nanorods for combined photothermal and chemotherapy

In this study, gold nanorods (AuNRs) were first stabilized by hexadecyltrimethylammonium bromide (CTAB) and then coated with two kinds of polyelectrolytes (PE) and BSA to obtain multi-layered AuNRs (AuNRs-PE-BSA). Furthermore, the anti-cancer drug doxorubicin (DOX) was encapsulated into AuNRs-PE-BSA by the electrostatic force and the nanocomposites formed were named AuNRs/DOX-PE-BSA. The success of coating was verified by transmission electron microscopy (TEM), zeta potential, gel-electrophoresis and thermogravimetric analysis (TGA). The MTT assay indicated that the cytotoxicity of AuNRs decreased dramatically after multi-layer capping. The time-dependent nucleus-targeting capability of AuNRs/DOX-PE-BSA was confirmed in cell affinity evaluations. The in vitro and in vivo experiments demonstrated that AuNRs/DOX-PE-BSA, which combined photothermal and chemotherapy for tumor therapy, bears a markedly improved curative effect and holds promising prospects in the field of nanomedicine.

Controlled synthesis of FePt-Au hybrid nanoparticles triggered by reaction atmosphere and FePt seeds

We report an effective and facile method for synthesis of FePt-Au hybrid nanoparticles (HNPs). The typical secondary growth of Au proceeded in the presence of FePt seeds in organic solvents under a specific atmosphere. Interestingly, the type of atmosphere (Ar or Ar-H₂) and the size of selected FePt seeds were two major parameters determining the final morphology of FePt-Au HNPs. Enhancement of catalytic activity and stability of FePt-Au HNPs in methanol oxidation were achieved owing to interactions between Au and FePt. The optical properties of the resulting products can be steadily tuned which sheds light on their potential application in optical devices and bioimaging. The novel synthetic strategy offers an important tool towards multifunctional nanomaterials with designed architectures.

Gold nanorods and their plasmonic properties

Gold nanorods have been receiving extensive attention owing to their extremely attractive applications in biomedical technologies, plasmon-enhanced spectroscopies, and optical and optoelectronic devices. The growth methods and plasmonic properties of Au nanorods have therefore been intensively studied. In this review, we present a comprehensive overview of the flourishing field of Au nanorods in the past five years. We will focus mainly on the approaches for the growth, shape and size tuning, functionalization, and assembly of Au nanorods, as well as the methods for the preparation of their hybrid structures. The plasmonic properties and the associated applications of Au nanorods will also be discussed in detail.

Highly ordered Fe-Au heterostructured nanorod arrays and their exceptional near-infrared plasmonic signature

The potential of highly ordered array nanostructures in sensing applications is well recognized, particularly with the ability to define the structural composition and arrangement of the individual nanorods accurately. The use of heterogeneous nanostructures generates an additional degree of freedom, which can be used to tailor the optical response of such arrays. In this article, we report on the fabrication and characterization of well-defined Fe-Au bisegmented nanorod arrays in a repeating hexagonal arrangement. Through an asymmetric etching method, free-standing Fe-Au nanorod arrays on a gold-coated substrate were produced with an inter-rod spacing of 26 nm. This separation distance renders the array capable of sustaining resonant electromagnetic wave coupling between individual rods. Owing to this coupling, the subwavelength arrangement, and the structural heterogeneity, the nanorod arrays exhibit unique plasmonic responses in the near-infrared (NIR) range. Enhanced sensitivity in this spectral region has not been identified for gold-only nanorods of equivalent dimensions. The NIR response offers confirmation of the potential of these highly ordered, high-density arrays for biomedical relevant applications, such as subcutaneous spectroscopy and biosensing.