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.

Systematic spectroscopic investigation of structural changes and corona formation of bovine serum albumin over magneto-fluorescent nanoparticles

Magneto-fluorescent nanoparticles have attracted great attention because of their dual nature as multimodal imaging probes in various biomedical applications. Particulary, it is desirable to understand how these nanoparticles interact with human serum proteins before they are used in biological systems. In this work, the physiological interactions between magneto-fluorescent nanoparticles (MFNPs) and bovine serum albumin (BSA) were systematically investigated. The present observations identified that the collision of MFNPs and BSA caused fluorescence quenching of BSA. Steady state fluorescence, lifetime and anisotropy measurements in the presence of MFNPs supported dynamic quenching of the BSA emission. Furthermore, in the presence of MFNPs, the conformation changes in the BSA structure indicate merely the secondary structural changes. The findings demonstrated that random interactions and hydrophobic forces play a major role in the dynamic quenching. Further, subsequent coating of BSA over MFNPs result in protein corona formation, as is evident through spectroscopic measurements. In light of the present work, MFNPs could serve a purpose in magnetic separation and optical detection of serum proteins from blood plasma in real-time disease diagnosis.

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.

Optical-Based (Bio) Sensing Systems Using Magnetic Nanoparticles

In recent years, various reports related to sensing application research have suggested that combining the synergistic impacts of optical, electrical or magnetic properties in a single technique can lead to a new multitasking platform. Owing to their unique features of the magnetic moment, biocompatibility, ease of surface modification, chemical stability, high surface area, high mass transference, magnetic nanoparticles have found a wide range of applications in various fields, especially in sensing systems. The present review is comprehensive information about magnetic nanoparticles utilized in the optical sensing platform, broadly categorized into four types: surface plasmon resonance (SPR), surface-enhanced Raman spectroscopy (SERS), fluorescence spectroscopy and near-infrared spectroscopy and imaging (NIRS) that are commonly used in various (bio) analytical applications. The review also includes some conclusions on the state of the art in this field and future aspects.

Synthesis and Morphological Control of Biocompatible Fluorescent/Magnetic Janus Nanoparticles Based on the Self-Assembly of Fluorescent Polyurethane and Fe₃O₄ Nanoparticles

Functionalized Janus nanoparticles have received increasing interest due to their anisotropic shape and the particular utility in biomedicine areas. In this work, a simple and efficient method was developed to prepare fluorescent/magnetic composite Janus nanoparticles constituted of fluorescent polyurethane and hydrophobic nano Fe₃O₄. Two kinds of fluorescent polyurethane prepolymers were synthesized by the copolymerization of fluorescent dye monomers, and the fluorescent/magnetic nanoparticles were fabricated in one-pot via the process of mini-emulsification and self-assembly. The nanostructures of the resulting composite nanoparticles, including core/shell and Janus structure, could be controlled by the phase separation in assembly process according to the result of transmission electron microscopy, whereas the amount of the nonpolar segments of polyurethane played an important role in the particle morphology. The prominent magnetic and fluorescent properties of the Janus nanoparticles were also confirmed by vibrating magnetometer and confocal laser scanning microscope. Furthermore, the Janus nanoparticles featured excellent dispersity, storage stability, and cytocompatibility, which might benefit their potential application in biomedical areas.

Effect of superparamagnetic nanoparticles coated with various electric charges on α-synuclein and β-amyloid proteins fibrillation process

Background

Most of nanoparticles are nontoxic and have high absorption capability. Therefore, nanoparticles binding can effectively restrain fibrillation of β-amyloid and α-synuclein proteins and eventually prevent the toxicity of pathogenesis peptide of Alzheimer. Super paramagnetic iron oxide nanoparticles (SPIONs) contain iron oxide core which can be connected to a special part through magnetic coating.

Materials and methods

In this study, the effect of SPIONs with different charges was simultaneously examined on the fibrillation of both β-amyloid and α-synuclein proteins by applying Thioflavin-T assay.

Results

According to the results of the investigation on amyloid-fibrillation mechanism in both β-amyloids and α-synucleins, it was revealed that negatively-charged nanoparticles encoded to –COOH by dextran-coating were able to have a considerable absorption decrease from 17,000–12,000 after 320 minutes delay to lag phase and decrease in binding level of thioflavin-T particles to β-sheets.

Conclusion

The different concentrations of these nanoparticles and special coating of each particle had an effect on the kinetics of β-amyloid and α-synuclein fibrillations.

Signatures of consolidated superparamagnetic and spin-glass behavior in magnetite-silver core-shell nanoparticles

A detailed investigation of magnetization relaxation for silver-coated magnetite nanostructures with three different types of magnetic behavior in a single particle is presented. Magnetite nanoparticles of diameter ∼6.5 nm synthesized via single-phase emulsion were further coated with a silver shell of thickness ∼2 nm. The synthesized nanoparticles are found to be efficiently photoluminescent. The coating of silver generates a magnetically disordered spin layer at the interface of the magnetic core and the non-magnetic shell. This intermediate layer plays a significant role in the dynamical magnetic response of nanoparticles under an external magnetic field. We present detailed magnetic measurements such as field- and temperature-dependent dc magnetization with zero-field-cooled and field-cooled protocols, ac susceptibility and time decay of magnetization relaxation along with their analysis using various formalisms viz. Néel-Arrhenius, Vogel-Fulcher and power law models. The relaxation analysis suggests the consolidated presence of two characteristic relaxation times corresponding to the superparamagnetic and spin-glass behavior of silver-coated magnetite nanoparticles.

Theranostic applications of nanoparticles in neurodegenerative disorders

The preeminent treatments for neurodegenerative disease are often unavailable due to the poor accessibility of therapeutic drugs. Moreover, the blood–brain barrier (BBB) effectively blocks the transfer of cells, particles and large molecules, ie, drugs, across the brain. The most important challenge in the treatment of neurodegenerative diseases is the development of targeted drug delivery system. Theranostic strategies are known to combine therapeutic and diagnostic capabilities together. The aim of this review was to record the response to treatment and thereby improve drug safety. Nanotechnology offers a platform for designing and developing theranostic agents that can be used as an efficient nano-carrier system. This is achieved by the manipulation of some of the properties of nanoparticles (NPs), thereby enabling the attachment of suitable drugs onto their surface. The results provide revolutionary treatments by stimulation and thus interaction with targeted sites to promote physiological response with minimum side effects. This review is a brief discussion of the administration of drugs across the brain and the advantages of using NPs as an effective theranostic platform in the treatment of Alzheimer’s, Parkinson’s, epilepsy and Huntington’s disease.

Carbon coated core-shell multifunctional fluorescent SPIONs

Due to their unique magnetic properties, multiple surface functionality and biocompatibility, superparamagnetic iron oxide nanoparticles (SPIONs) show very promising characteristics as magnetic resonance (MR) contrast agents in biomedical applications. However, a lack of fluorescence makes SPIONs inappropriate for multimodal bioimaging. SPIONs surface functionalized by either organic fluorescent molecules or semiconductor quantum dots (QDs) have been reported as bioimaging probes but subsequent deterioration of the fluorescent dyes due to low photostability and quick photobleaching limits their long term practical application. In addition, QDs are found to be toxic in nature. Here, we present a novel one step method to synthesize non-toxic carbon coated highly photostable core-shell magnetic and fluorescent SPIONs with long-lasting fluorescence alongside a superior magnetic resonance (MR) imaging ability. Apart from the highly comparable superparamagnetic properties of the SPIONs, the optical response of the material is much better than commonly used Rhodamine or cyanine dyes.

Iron Oxide Nanoparticles Labeled with an Excited-State Intramolecular Proton Transfer Dye

Excited-state intramolecular proton transfer (ESIPT) is a particularly well known reaction that has been very little studied in magnetic environments. In this work, we report on the photophysical behavior of a known ESIPT dye of the benzothiazole class, when in solution with uncoated superparamagnetic iron oxide nanoparticles, and when grafted to silica-coated iron oxide nanoparticles. Uncoated iron oxide nanoparticles promoted the fluorescence quenching of the ESIPT dye, resulting from collisions during the lifetime of the excited state. The assembly of iron oxide nanoparticles with a shell of silica provided recovery of the ESIPT emission, due to the isolation promoted by the silica shell. The silica network gives protection against the fluorescence quenching of the dye, allowing the nanoparticles to act as a bimodal (optical and magnetic) imaging contrast agent with a large Stokes shift.

One-pot synthesis of carbon dot-entrenched chitosan-modified magnetic nanoparticles for fluorescence-based Cu2+ ion sensing and cell imaging

In this work, a new synthetic approach is developed for the synthesis of fluorescent magnetic nanoparticles which are explored for the detection of mostly abundant transition metal Cu²⁺ ions and cell imaging.

Iron oxide-based multifunctional nanoparticulate systems for biomedical applications: a patent review (2008 - present)

INTRODUCTION

Iron oxide nanoparticles (IO NPs) exhibit remarkable properties, including inherent magnetism, biocompatibility, high surface to volume ratio, and versatility of engineering, making them ideal candidates for a variety of clinical applications.

AREAS COVERED

The review provides an in-depth discussion on recent patents and developments related to IO NPs in Biomedicine from the last 7 years. It covers innovations in the chemical synthesis, surface coating and functionalization, and biomedical applications, including MRI and multimodal imaging, molecular imaging, cell labeling, drug delivery, hyperthermia, hyperphosphatemia, and antibacterial activity. A brief outline of the important properties of IO NPs is also presented.

EXPERT OPINION

The main focus of current research is the development of new approaches to generate high-quality IO NPs with optimal properties in terms of particle geometry, crystal structure, surface functionalities, stability, and magnetization. Among chemical synthesis methods, thermal decomposition and hydrothermal synthetics processes allow fine control of the particle properties. Plenty of coating materials have been successfully used as shells for these NPs to provide colloidal stability, even enabling the formulation of nanotheranostics for simultaneous disease diagnosis and therapy. However, long-term toxicity and pharmacokinetic studies are necessary before magnetic nanosystems can be approved for clinical use.

Inorganic nanovehicle for potential targeted drug delivery to tumor cells, tumor optical imaging

In this work, an inorganic multifunctional nanovehicle was tailored as a carrier to deliver anticancer drug for tumor optical imaging and therapy. The nanovehicle could be used as a dually targeted drug nanovehicle by bonded magnetical (passive) and folic acid (active) targeting capabilities. In addition, it was developed using rhodamine 6G (R6G) as a fluorescence reagent, and an α-zirconium phosphate nanoplatform (Zr(HPO4)2·H2O, abbreviated as α-ZrP) as the anticancer drug nanovehicle. The novel drug-release system was designed and fabricated by intercalation of α-ZrP with magnetic Fe3O4 nanoparticles and anticancer drug 5-fluorouracil (5-FU), followed by reacting with a folate acid-chitosan-rhodamine6G (FA-CHI-R6G) complex, and then α-ZrP intercalated with Fe3O4 nanoparticles and 5-fluorouracil (5-FU) was successfully encapsulated into chitosan (CHI). The resultant multifunctional drug delivery system was characterized by scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray analysis, photoluminescence spectra, magnetometry, fluorescence microscopy imaging studies and other characterization methods. Simultaneously, the drug release in vitro on the obtained nanocomposites that exhibited a sustained release behavior was carried out in buffer solution at 37 °C, which demonstrated clearly that the nanocomposites shown a sustained release behavior. Meanwhile, cell culture experiments also indicated that the drug-release system had the potential to be used as an dually targeted drug nanovehicle into the tumor cells.

Metal-enhanced fluorescence-based core-shell Ag@SiO₂ nanoflares for affinity biosensing via target-induced structure switching of aptamer

One of the great challenges in metal-enhanced fluorescence (MEF) technology is the achievement of distance modulation with nanometer accuracy between the fluorophore and metal surface to obtain maximum enhancement. We propose an MEF-based core-shell Ag@SiO2 nanoflare for distance control via the thickness of silica shell with cooperation of DNA hybridization. The nanoflare contains a 50 nm spherical silver nanoparticle (Ag NP) core, a 8 nm silica shell, and cyanine (Cy5)-labeled aptamer hybridized with a complementary DNA (cDNA) immobilized onto the shell surface. The formation of the Cy5-labeled aptamer/cDNA duplex on the Ag@SiO2 NP surface results in the confinement of Cy5 to the shell surface and an increase in the fluorescence of Cy5 with a 32-fold enhancement factor in bulk solution (signal-on). In the presence of affinity-binding targets, the Cy5-labeled aptamers confined onto the Ag@SiO2 NP surface dissociate from their cDNA into the solution because of structure switching. The target-induced release of aptamer leads to a reduction in the enhanced fluorescence signal of the labeled Cy5 moiety (signal-off). Thus, the nanoflare can be used as a sensor for target recognition. Using adenosine-5'-triphosphate (ATP) aptamer, detection of ATP has a linear response from 0 to 0.5 mM and a detection limit of 8 μM. With various types of DNA probes immobilized onto the core-shell Ag@SiO2 NPs, the MEF-based nanoflare has provided an effective platform for the detection and quantification of a broad range of analytes, such as mRNA regulation and detection, cell sorting, and gene profiling.

Exocytosis of nanoparticles from cells: role in cellular retention and toxicity

Over the past decade, nanoparticles (NPs) have been increasingly developed in various biomedical applications such as cell tracking, biosensing, contrast imaging, targeted drug delivery, and tissue engineering. Their versatility in design and function has made them an attractive, alternative choice in many biological and biomedical applications. Cellular responses to NPs, their uptake, and adverse biological effects caused by NPs are rapidly-growing research niches. However, NP excretion and its underlying mechanisms and cell signaling pathways are yet elusive. In this review, we present an overview of how NPs are handled intracellularly and how they are excreted from cells following the uptake. We also discuss how exocytosis of nanomaterials impacts both the therapeutic delivery of nanoscale objects and their nanotoxicology.

Alzheimer's disease: pathophysiology and applications of magnetic nanoparticles as MRI theranostic agents

Alzheimer's disease (AD) is the most common form of dementia. During the recent decade, nanotechnology has been widely considered, as a promising tool, for theranosis (diagnosis and therapy) of AD. Here we first discuss pathophysiology and characteristics of AD with a focus on the amyloid cascade hypothesis. Then magnetic nanoparticles (MNPs) and recent works on their applications in AD, focusing on the superparamagnetic iron oxide nanoparticles (SPIONs), are reviewed. Furthermore, the amyloid-nanoparticle interaction is highlighted, with the scope to be highly considered by the scientists aiming for diagnostics and/or treatment of AD employing nanoparticles. Furthermore, recent findings on the "ignored" parameters (e.g., effect of protein "corona" at the surface of nanoparticles on amyloid-β (Aβ) fibrillation process) are discussed.

Multifunctional nanoparticles for targeted delivery of immune activating and cancer therapeutic agents

Nanoparticles (NPs) have been extensively investigated for applications in both experimental and clinical settings to improve delivery efficiency of therapeutic and diagnostic agents. Most recently, novel multifunctional nanoparticles have attracted much attention because of their ability to carry diverse functionalities to achieve effective synergistic therapeutic treatments. Multifunctional NPs have been designed to co-deliver multiple components, target the delivery of drugs by surface functionalization, and realize therapy and diagnosis simultaneously. In this review, various materials of diverse chemistries for fabricating multifunctional NPs with distinctive architectures are discussed and compared. Recent progress involving multifunctional NPs for immune activation, anticancer drug delivery, and synergistic theranostics is the focus of this review. Overall, this comprehensive review demonstrates that multifunctional NPs have distinctive properties that make them highly suitable for targeted therapeutic delivery in these areas.

Quantum dots incorporated magnetic nanoparticles for imaging colon carcinoma cells

Background

Engineered multifunctional nanoparticles (NPs) have made a tremendous impact on the biomedical sciences, with advances in imaging, sensing and bioseparation. In particular, the combination of optical and magnetic responses through a single particle system allows us to serve as novel multimodal molecular imaging contrast agents in clinical settings. Despite of essential medical imaging modalities and of significant clinical application, only few nanocomposites have been developed with dual imaging contrast. A new method for preparing quantum dots (QDs) incorporated magnetic nanoparticles (MNPs) based on layer-by-layer (LbL) self-assembly techniques have developed and used for cancer cells imaging.

Methods

Here, citrate - capped negatively charged Fe₃O₄ NPs were prepared and coated with positively - charged hexadecyltrimethyl ammonium bromide (CTAB). Then, thiol - capped negatively charged CdTe QDs were electrostatically bound with CTAB. Morphological, optical and magnetic properties of the fluorescent magnetic nanoparticles (FMNPs) were characterized. Prepared FMNPs were additionally conjugated with hCC49 antibodies fragment antigen binding (Fab) having binding affinity to sialylated sugar chain of TAG-72 region of LS174T cancer cells, which was prepared silkworm expression system, and then were used for imaging colon carcinoma cells.

Results

The prepared nanocomposites were magnetically responsive and fluorescent, simultaneously that are useful for efficient cellular imaging, optical sensing and magnetic separation. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) revealed that the particle size is around 50 nm in diameter with inner magnetic core and outer CdTe QDs core-shell structure. Cytotoxicity test of prepared FMNPs indicates high viability in Vero cells. NPs conjugated with anti cancer antibodies were successfully labeled on colon carcinoma cells (LS174) in vitro and showed significant specificity to target cells.

Conclusion

The present report demonstrates a simple synthesis of CdTe QDs-Fe₃O₄ NPs. The surface of the prepared FMNPs was enabled simple conjugation to monoclonal antibodies by electrostatic interaction. This property further extended their in vitro applications as cellular imaging contrast agents. Such labeling of cells with new fluorescent-magneto nanoprobes for living detection is of interest to various biomedical applications and has demonstrated the potential for future medical use.

Multifunctional PEGylated nanoclusters for biomedical applications

A simple and versatile synthesis method to form water soluble multifunctional nanoclusters using polyethylene glycol (PEG) functionalized poly(maleic anhydride-alt-1-octadecene) amphiphilic brush copolymers (PMAO-g-PEG) was presented. Simply by tuning the core size and the initial nanocrystal concentration, manganese ferrite nanoparticles (MFNPs) were used to demonstrate the versatility of tuning the loading amount of the nanoclusters. The resultant nanoclusters were found to have a well-controlled spherical shape. When Zn-doped AgInS2 quantum dots (AIZS QDs) were loaded together with the MFNP nanocrystals, bi-functional nanoclusters with fluorescent and magnetic behaviors were obtained. Such bi-functional nanoclusters were also successfully demonstrated for cellular bio-imaging. Moreover, the presence of another type of nanocrystals together with MFNPs was found to have a negligible effect on the overall properties of the nanoclusters as demonstrated by the MR relaxivity test. From the time-dependent colloidal stability test, it was found that the presence of the PEG chain grafted onto PMAO was able to reduce protein adsorption onto the nanocluster surface. An in vitro study on NIH/3T3 demonstrated the biocompatibility of the nanoclusters. Such biocompatible and colloidally stable nanoclusters with an approximate size of 80-120 nm were suitable for both MRI and cell labeling applications.

Fluorescent pH sensor based on Ag@SiO2 core-shell nanoparticle

We have demonstrated a novel method for the preparation of a fluorescence-based pH sensor by combining the plasmon resonance band of Ag core and pH sensitive dye (HPTS). A thickness-variable silica shell is placed between Ag core and HPTS dye to achieve the maximum fluorescence enhancement. At the shell thickness of 8 nm, the fluorescence intensity increases 4 and 9 times when the sensor is excited at 405 and 455 nm, respectively. At the same time, the fluorescence intensity shows a good sensitivity toward pH value in the range of 5-9, and the ratio of emission intensity at 513 nm excited at 455 nm to that excited at 405 nm versus the pH value in the range of 5-9 is determined. It is believed that the present pH sensor has the potential for determining pH real time in the biological sample.

Influence of the physiochemical properties of superparamagnetic iron oxide nanoparticles on amyloid β protein fibrillation in solution

Superparamagnetic iron oxide nanoparticles (SPIONs) are recognized as promising nanodiagnostic materials due to their biocompatibility, unique magnetic properties, and their application as multimodal contrast agents. As coated SPIONs have potential use in the diagnosis and treatment of various brain diseases such as Alzheimer's, a comprehensive understanding of their interactions with Aβ and other amyloidogenic proteins is essential prior to their clinical application. Here we demonstrate the effect of thickness and surface charge of the coating layer of SPIONs on the kinetics of fibrillation of Aβ in aqueous solution. A size and surface area dependent "dual" effect on Aβ fibrillation was observed. While lower concentrations of SPIONs inhibited fibrillation, higher concentrations increased the rate of Aβ fibrillation. With respect to coating charge, it is evident that the positively charged SPIONs are capable of promoting fibrillation at significantly lower particle concentrations compared with negatively charged or uncharged SPIONs. This suggests that in addition to the presence of particles, which affect the concentration of monomeric protein in solution (and thereby the nucleation time), there are also effects of binding on the protein conformation.