Assembly Of Iron Oxide Nanoparticles Research Articles

Metal-Organic Framework as a New Type of Magnetothermally-Triggered On-Demand Release Carrier.

The development of external stimuli-controlled payload systems has been sought after with increasing interest toward magnetothermally-triggered drug release (MTDR) carriers due to their non-invasive features. However, current MTDR carriers present several limitations, such as poor heating efficiency caused by the aggregation of iron oxide nanoparticles (IONPs) or the presence of antiferromagnetic phases which affect their efficiency. Herein, a novel MTDR carrier is developed using a controlled encapsulation method that fully fixes and confines IONPs of various sizes within the metal-organic frameworks (MOFs). This novel carrier preserves the MOF's morphology, porosity, and IONP segregation, while enhances heating efficiency through the oxidation of antiferromagnetic phases in IONPs during encapsulation. It also features a magnetothermally-responsive nanobrush that is stimulated by an alternating magnetic field to enable on-demand drug release. The novel carrier shows improved heating, which has potential applications as contrast agents and for combined chemo and magnetic hyperthermia therapy. It holds a great promise for magneto-thermally modulated drug dosing at tumor sites, making it an exciting avenue for cancer treatment.

Unveiling the Biologically Dynamic Degradation of Iron Oxide Nanoparticles via a Continuous Flow System.

Nanomaterials are increasingly being employed for biomedical applications, necessitating a comprehensive understanding of their degradation behavior and potential toxicity in the biological environment. This study utilizes a continuous flow system to simulate the biologically relevant degradation conditions and investigate the effects of pH, protein, redox species, and chelation ligand on the degradation of iron oxide nanoparticles. The morphology, aggregation state, and relaxivity of iron oxide nanoparticles after degradation are systematically characterized. The results reveal that the iron oxide nanoparticles degrade at a significantly higher rate under the acidic environment. Moreover, incubation with bovine serum albumin enhances the stability and decreases the dissolution rate of iron oxide nanoparticles. In contrast, glutathione accelerates the degradation of iron oxide nanoparticles, while the presence of sodium citrate leads to the fastest degradation. This study reveals that iron oxide nanoparticles undergo degradation through various mechanisms in different biological microenvironments. Furthermore, the dissolution and aggregation of iron oxide nanoparticles during degradation significantly impact their relaxivity, which has implications for their efficacy as magnetic resonance imaging contrast agents in vivo. The results provide valuable insights for assessing biosafety and bridge the gap between fundamental research and clinical applications of iron oxide nanoparticles.

Specific absorption rate of randomly oriented magnetic nanoparticles in a static magnetic field.

Numerical simulations using the stochastic Landau-Lifshitz equation are performed to study magnetization dynamics of dilute assemblies of iron oxide nanoparticles exposed to an alternating (ac) magnetic field with an amplitude H ac = 200 Oe and a frequency f = 300 kHz and a static (dc) magnetic field in the range H dc = 0-800 Oe. The specific absorption rate (SAR) of the assemblies is calculated depending on the angle between the directions of the ac and dc magnetic fields. For the case of an inhomogeneous dc magnetic field created by two opposite magnetic fluxes, the spatial distribution of the SAR in the vicinity of the field-free point is obtained for assemblies with different nanoparticle size distributions. The results obtained seem to be helpful for the development of a promising joint application of magnetic nanoparticle imaging and magnetic hyperthermia.

Hypoxia-Responsive Aggregation of Iron Oxide Nanoparticles for T1-to-T2 Switchable Magnetic Resonance Imaging of Tumors

Magnetic resonance imaging (MRI), one of the most general imaging techniques in the clinic, is widely employed for tumor diagnosis with the assistance of contrast agents (CAs). However, currently available CAs in the clinic suffer from shortcomings of a short blood circulation time, lack of specificity to pathological location, insufficient imaging window, and potential biotoxicity of the gadolinium ion. To overcome these problems, on the basis of extremely small iron oxide nanoparticles (ESIONPs), a hypoxia-responsive T1-to-T2 switchable MRI contrast agent was designed and constructed. In detail, polyacrylic acid-modified ESIONPs (ESIONPs-PAA) were first synthesized, and then, nitroimidazole derivatives and cysteine molecules were sequentially coupled on the surface of ESIONPs-PAA to obtain a hypoxia-responsive MRI contrast agent (HR-ESIONPs). Since 2-nitroimidazole and cysteine molecules on the surface of HR-ESIONPs can form an irreversible bond induced by the nitroreductase in the hypoxic tumor microenvironment, monodispersed HR-ESIONPs could transform into the nanocluster form, which can specially provide T2 contrast enhancement. In vitro experiments show that monodispersed HR-ESIONPs could effectively aggregate in the mimical hypoxic environment of tumors and switch from a T1 to T2 contrast agent. Moreover, in vivo experiments further confirm that HR-ESIONPs could effectively accumulate and realize the MRI signal switch from T1 to T2 contrast enhancement in tumors originating from the aggregation of HR-ESIONPs induced by the hypoxic environment, which promotes the diagnostic precision of tumors. Additionally, with the confirmation of favorable biosafety on cells and mice, hypoxia-responsive HR-ESIONPs are potential platforms to improve the diagnostic accuracy and sensitivity of MRI for tumors.

Stimuli-controllable iron oxide nanoparticle assemblies: Design, manipulation and bio-applications.

Despite its wide establishment over the years, iron oxide nanoparticle (IONP) still draws extensive interest in the biomedical fields due to its biocompatibility, biodegradability, magnetivity and surface tunable properties. IONP has been used for the MRI, magnetic targeting, drug delivery and hyperthermia of various diseases. However, their poor stability, low diagnostic sensitivity and low disease-specificity have resulted in unsatisfying diagnostic and therapeutic outputs. The surface functionalization of IONP with biocompatible and colloidally stable components appears to be promising to improve its circulation and colloidal stability. Importantly, through surface functionalization with designated functional components, IONP-based assemblies with multiple stimuli-responsivity could be formed to achieve an accurate and efficient delivery of IONP to disease sites for an improved disease diagnosis and therapy. In this work, we first described the design of biocompatible and stable IONP assemblies. Further, their stimuli-driven manipulation strategies are reviewed. Next, the utilization of IONP assemblies for disease diagnosis, therapy and imaging-guided therapy are discussed. Then, the potential toxicity of IONPs and their clinical usages are described. Finally, the intrinsic challenges and future outlooks of IONP assemblies are commented. This review provides recent insights into IONP assemblies, which could inspire researchers on the future development of multi-responsive and disease-targetable nanoassemblies for biomedical utilization.

Dual-Sensitive Gold-Nanocubes Platform with Synergistic Immunotherapy for Inducing Immune Cycle Using NIR-Mediated PTT/NO/IDO.

Currently, the combination therapies based on immunotherapy have been rapidly developed, but the response rate has not always increased as expected. Nano-platform has become a potential strategy which can trigger multi-functions to increase immunotherapeutic efficacy via activating T-cells and photothermal effect. Herein, to avoid the self-degradation and provide pH-sensitive property, S-nitrosoglutathione (GSNO) was loaded in gold nanocubes (AuNCs) with polyacrylic acid (PAA) coating. Subsequently, the layer-by-layer (LbL) assembly of iron oxide nanoparticles (Fe3O4) and betanin can provide the conjugation of 1-methyl-D-tryptophan (1-M-DT) on the nanoparticle to form an NO gas-photothermal-immune nano-platform (GAPFBD) for achieving combinatory therapy of NO gas, photothermal therapy (PTT), and indoleamine 2,3-dioxygenase (IDO) immunotherapy. After irradiation by 808-nm laser, the GSNO was released under a lower pH environment due to the structural transformation of PAA and then transformed into NO production of 64.5 ± 1.6% under PTT. The combination of PTT and NO gas therapy can effectively eliminate cancer cells, resulting in a large amount of tumor-associated antigens (TAAs) compared to the individual treatment in vitro. Additionally, the released 1-M-DT inhibited IDO and combined with TAAs to enhance maturation of dendritic cells (DCs), indicating the excellent synergistic effect of PTT and NO with IDO inhibitors. These results revealed that this dual-sensitive nanoparticle presented a combination strategy of PTT/NO/IDO for the synergistic effect to promote DC maturation.

Magnetically Induced Aggregation of Iron Oxide Nanoparticles for Carrier Flotation Strategies.

On the nanoscale, iron oxides can be used for multiple applications ranging from medical treatment to biotechnology. We aimed to utilize the specific properties of these nanoparticles for new process concepts in flotation. Magnetic nanoparticles were synthesized by alkaline coprecipitation, leading to a primary particle size of 9 nm, and coated with oleate. The nanomaterial was characterized for its superparamagnetism and its colloidal stability at different ionic strengths, with and without an external magnetic field. The nanomaterial was used for model experiments on magnetic carrier flotation of microplastic particles, based on magnetically induced heteroagglomeration. We were able to demonstrate the magnetically induced aggregation of the nanoparticles which allows for new flotation strategies. Since the nanomaterial has zero remanent magnetization, the agglomeration is reversible which facilitates the process control. Magnetic carrier flotation based on iron oxide nanoparticles can pave the way to promising new recycling processes for microplastic wastes.

Properties of assembly of superparamagnetic nanoparticles in viscous liquid

Detailed calculations of the specific absorption rate (SAR) of a dilute assembly of iron oxide nanoparticles with effective uniaxial anisotropy dispersed in a liquid are performed depending on the particle diameters, the alternating (ac) magnetic field amplitude H0 and the liquid viscosity. For small and moderate H0 values with respect to particle anisotropy field Hk the SAR of the assembly as a function of the particle diameter passes through a characteristic maximum and then reaches a plateau, whereas for sufficiently large amplitudes, H0 ~ Hk, the SAR increases monotonically as a function of diameter. The realization of viscous and magnetic oscillation modes for particle unit magnetization vector and director for moderate and sufficiently large H0 values, respectively, explains this behavior. It is found that the SAR of the assembly changes inversely with the viscosity only in a viscous mode, for nanoparticles of sufficiently large diameters. In the magnetic mode the SAR of the assembly is practically independent of the viscosity, since in this case the nanoparticle director only weakly oscillates around the ac magnetic field direction. The conditions for the validity of the linear response theory have been clarified by comparison with the numerical simulation data.

Stimuli-responsive assembly of iron oxide nanoparticles into magnetic flexible filaments

The combination of multiple functionalities in a single material is an appealing strategy for the development of smart materials with unique features. In this work, we present the preparation of thermoresponsive magnetic nanoparticles and their one-dimensional assembly into transient microfilaments. The material is based on 9.4 nm iron oxide nanoparticles grafted with poly(N-n-propylacrylamide) via multiphosphonic acid anchoring sites. The hybrid nanoparticles present a low critical solution temperature (LCST) transition between 21°C and 28°C, depending on the pH and the ionic strength. When heated above the LCST in defined conditions, the nanoparticles aggregate and respond to an external magnetic field. An intrinsic characteristic of the thermoresponsive particles is an asymmetric transition between cooling and heating cycles that was favorably exploited to build one-dimensional permanent microstructures, such as magnetic microfilaments and cilia. In summary, we present the development of a nanoplatform responsive to multiple stimuli, including temperature, magnetic field, pH, and ionic strength and its transformation into magnetically active microfilaments that could find potential applications in remotely controlled devices.

Nanostructured maghemite and magnetite and their nanocomposites with graphene oxide for photocatalytic degradation of methylene blue

A wet chemical route was utilized to synthesize iron oxide nanoparticles for the photocatalytic degradation of the Methylene Blue (MB) dye. The former (γ-Fe2O3) was also used to fabricate composite with graphene oxide (GO). X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) were used to confirm the prepared compounds and their composites with GO. XRD confirmed the crystalline structure with the corresponding patterns and other physical parameters. The wider peaks showed the less crystallite size of prepared samples. SEM images showed that the nanoparticles have relatively spherical morphology. The size estimated from the SEM images was in the range of 70–100 nm. The surface properties such as specific surface area and pore size were also determined by N2 adsorption-desorption measurements. The specific surface areas determined from BET analysis were 50 m2/g and 73 m2/g for iron oxide nanoparticles and their composite with GO, respectively. High surface area provided more attachment sites for the adsorption of methylene blue (MB) molecules with γ-Fe2O3 @ GO. Further GO suppressed the aggregation of iron oxide nanoparticles. UV spectroscopic analysis led towards band gap energy value which motivated the optical properties of the nanoparticles. As the nanodomain of particles was lowered, the band gap values increased. Therefore the efficacy of γ-Fe2O3 @ GO nanomaterials was improved. The photodegradation of MB by γ-Fe2O3 @ GO was observed up to 90.6% compared to γ-Fe2O3 and Fe3O4 nanoparticles. Easy electronic conduction from valence band to conduction band and suppression of charge carrier recombination at photocatalyst surface could also increase the photocatalytic activity of photocatalyst.

Hollow Mesoporous Silica Nanoparticles with Extra-Large Mesopores for Enhanced Cancer Vaccine.

Owing to the limitations of conventional cancer therapies, cancer immunotherapy has emerged for the prevention of cancer recurrence. To provoke adaptive immune responses that are antigen-specific, it is important to develop an efficient antigen delivery system that can enhance the activation and maturation of the dendritic cells (DCs) in the human body. In this study, we synthesize hollow mesoporous silica nanoparticles with extra-large mesopores (H-XL-MSNs) based on a single-step synthesis from core-shell mesoporous silica nanoparticles with a core composed of an assembly of iron oxide nanoparticles. The hollow void inside the mesoporous silica nanoparticles with large mesopores allows a high loading efficiency of various model proteins of different sizes. The H-XL-MSNs are coated with a poly(ethyleneimine) (PEI) solution to provide an immune adjuvant and change the surface charge of the particles for loading and slow release of a model antigen. An in vitro study using a cancer vaccine based on the PEI-coated H-XL-MSNs with the loading of the model antigen showed an enhanced activation of the DCs. An in vivo study demonstrated that the resulting cancer vaccine increased the antigen-specific cytotoxic T cells, enhanced the suppression of tumor growth, and improved the survival rate after challenging cancer to mice. These findings suggest that these hollow MSNs with extra-large pores can be used as excellent antigen carriers for immunotherapy.

Investigation of the structure of iron oxide nanoparticle assemblies in order to optimize the sensitivity of surface plasmon resonance-based sensors

Surface plasmon resonance (SPR) biosensors based on metal thin films are very attractive for detection of biomolecules. Nanoparticle assemblies were recently demonstrated to significantly enhance sensitivity. Here, we show that the fine control of the structure of nanoparticle assemblies is critical to optimize the sensitivity. Iron oxide (Fe3-δO4) nanoparticles were assembled onto a gold thin film by performing the Copper Catalyzed Alkyne-Azide cycloaddition (CuAAC) “click” reaction. A biotin derivative was grafted by CuAAC at the surface of nanoparticle assemblies in order to detect streptavidin (SA). The fine control of the size and of the density of nanoparticles allowed tuning the surface plasmon waves at the surface of the gold thin film in order to optimize the response of the sensors. The accessibility of biotin at the nanoparticle surface to SA was also investigated as a function of the interparticle distance. We show that the interplay between the volume fraction of iron oxide and the accessibility of biotin at the nanoparticle surface is critical to enhance the sensitivity of SPR sensors.

Programmable Assembly of Iron Oxide Nanoparticles Using DNA Origami.

Magnetic iron oxide nanoparticles (IONPs) have received significant interest for the use in biomedical applications. The assembly of IONPs into larger superstructures has been used to modify the properties and functionality of these particles. For example, the clustering of IONPs can lead to improvements in MRI contrast generation, changes in heat generation during magnetic fluid hyperthermia, and alterations to pharmacokinetics and biodistribution. Nevertheless, the IONP clustering leads to significant heterogeneity in the assembly. Here, we demonstrate a method for using DNA origami to precisely control the number and positions of IONPs. We also showed how this technique can be used to module the functionality of IONP clusters by showing how MRI contrast generation efficiency can be tuned by altering the number and spacing of IONPs. Finally, we show that these property changes can be dynamically regulated, demonstrating the possibility for this technology to be used in biosensing applications.

Defect‐Driven Magnetization Configuration of Isolated Linear Assemblies of Iron Oxide Nanoparticles

AbstractThe magnetization state of 1D magnetic nanoparticle (NP) chains plays a key role in a wide range of applications ranging from diagnosis and therapy in medicine to actuators, sensors, and quantum recording media. The interplay between the exact particle orientation and the magnetic anisotropy is in turn crucial for controlling the overall magnetization state with high precision. Here, a 3D description of the magnetic structure of one‐NP‐wide chains is reported. Here, two complementary experimental techniques are combined, magnetic force microscopy (MFM) and electronic holography (EH) which are sensitive to out‐of‐plane and in‐plane magnetization components, respectively. The approach to micromagnetic simulations is extended, which provides results in good agreement with MFM and EH. The findings are at variance with the known results on unidirectional NP assemblies, and show that magnetization is rarely strictly collinear to the chain axis. The magnetic structure of one‐NP‐wide chains can be interpreted as head‐to‐head magnetic domain structures with off‐axis magnetization components, which is very sensitive to morphological defects in the chain structure such as minute size variation of NPs, tiny misalignment of NPs, and/or crystal orientation with respect to easy magnetization axis.

Facile fabrication of iron oxide/carbon/rGO superparamagnetic nanocomposites for enhanced electrochemical energy storage performance

To develop iron-based materials for energy storage is an important issue because of their low cost, abundant storage and high theoretical specific capacitances. Fe(OH)3 colloids stabilized by FeCl3 are used as the precursor to fabricate with carbon from glucose and graphene oxide (GO) to prepare superparamagnetic iron oxide/carbon/rGO (reduced graphene oxide) composite for enhanced energy storage performance. Glucose or graphene oxide cannot avoid the aggregation of iron oxides when they are used separately; however, the simultaneous addition of glucose and graphene oxide can supress the aggregation of iron oxide nanoparticles, which is beneficial for energy storage. The characterization results of Fe2O3-based composites, including XRD, TEM and XPS, reveal that iron oxide nanocrystals in the composites are γ-Fe2O3. The simultaneous utilization of GO and glucose leads to higher saturation magnetizations of iron oxide than GO or glucose does, and the saturation magnetization of iron oxide in the iron oxide/carbon/rGO composite can be up to 83 emu g−1. More importantly, the iron oxide/carbon/rGO composites have much higher energy storage performance than that of iron oxide/carbon or iron oxide/rGO samples. The specific capacitance of the composites can reach 400 F g−1 and the retention can remain 92% after 2500 cycles.

Iron Oxide Nanoparticles for Magnetic Hyperthermia

Assemblies of magnetic nanoparticles show a great potential for application in biomedicine, particularly, magnetic hyperthermia. However, to achieve desired therapeutic effect in magnetic hyperthermia, the assembly of nanoparticles should have a sufficiently high specific absorption rate (SAR) in alternating magnetic field of moderate amplitude and frequency. Using the Landau–Lifshitz stochastic equation, it is shown that dilute assemblies of iron oxide nanoparticles of optimal diameters are capable of providing SAR of the order of 400–600[Formula: see text]W/g in alternating magnetic field with the amplitude [Formula: see text][Formula: see text]Oe in the frequency range f = 300–500[Formula: see text]kHz. Unfortunately, in dense clusters of magnetic nanoparticles, which are often formed in a biological medium, there is a sharp decrease in SAR due to the influence of strong magneto-dipole interaction of closest nanoparticles. To overcome this difficulty, it is suggested covering the nanoparticles with nonmagnetic shells of sufficient thickness or using non-single-domain nanoparticles being in magnetization curling states.

Magnetically Actuated Dynamic Iridescence Inspired by the Neon Tetra.

Inspired by the tropical fish neon tetra, we report a mechanism to achieve dynamic iridescence that can be magnetically tuned. This approach is based on the tilting of periodic photonic nanostructures, as opposed to the more common strain-induced color tuning. In this method, a periodic array of magnetic nanopillars serves as a template to guide the assembly of iron oxide nanoparticles when magnetized in a liquid environment. The periodic local fields induced by the magnetic template anchor the assembled particle columns, allowing the structure to tilt about the base when the angle of the applied field is changed. This effect emulates a microscopic "Venetian blind" and results in dynamic optical properties through structural coloration that is tunable in real time. The fabricated prototype demonstrates tunable reflectance spectra with peak wavelength shift from 528 to 720 nm. The magnetic actuation mechanism is reversible and has a fast response time around 0.3 s. This structure can be implemented on an arbitrary surface as dynamic camouflage, iridescent display, and tunable photonic elements, as well as in other applications such as active fluidic devices and particle manipulation.

Dynamically Reversible Iron Oxide Nanoparticle Assemblies for Targeted Amplification of T1-Weighted Magnetic Resonance Imaging of Tumors.

Smart magnetic resonance (MR) contrast agents, by which MR contrast can be selectively enhanced under acidic tumor microenvironment, are anticipated to significantly improve the diagnostic accuracy. Here, we report pH-sensitive iron oxide nanoparticle assemblies (IONAs) that are cross-linked by small-molecular aldehyde derivative ligands. The dynamic formation and cleavage of hydrazone linkages in neutral and acidic environments, respectively, allow the reversible response of the nanoassemblies to pH variations. At neutral pH, IONAs are structurally robust due to the cross-linking by the strong hydrazone bonds. In acidic tumor microenvironment, the hydrazone bonds are cleaved so that the IONAs are quickly disassembled into a large number of hydrophilic extremely small-sized iron oxide nanoparticles (ESIONs). As a result, significantly enhanced T1MR contrast is achieved, as confirmed by the measurement of r1 values at different pH conditions. Such acidity-targeting MR signal amplification by the pH-sensitive IONAs was further validated in vivo, demonstrating a novel T1 magnetic resonance imaging (MRI) strategy for highly sensitive imaging of acidic tumors.

Manipulation of dipolar magnetism in low-dimensional iron oxide nanoparticle assemblies.

The manipulation of magnetic states in nanoparticle supercrystals promises new pathways to design nanocrystalline magnetic materials and devices. Trench-patterned silicon substrates were used as templates to guide the self-assembly of iron oxide nanoparticles. Grazing incidence small angle X-ray scattering shows that the nanoparticles form a long-range ordered structure along the trench direction while in the direction perpendicular to the trenches, no coherent structure is observable. Electron holography provides evidence of an ordered magnetic state of nanoparticle moments in the remanent state after the application of a saturation magnetic field parallel to the trenches. However, a disordered magnetic state was observed in a perpendicular geometry. Hysteresis loops indicate that the nanoparticle moments form a superferromagnetic state for the geometry parallel to the trenches. Memory effect investigations reveal that the disordered magnetic state corresponds to a collective superspin glass state in the perpendicular geometry, while the superferromagnetic state in the parallel geometry suppresses the superspin glass state.

Ordered assemblies of Fe3O4 and a donor-acceptor-type π-conjugated polymer in nanoparticles for enhanced photoacoustic and magnetic effects

We report that the ordered structure in the assemblies of iron oxide nanoparticles in conjugated polymer nanoparticles is the key to achieve better properties to realize multimodal theranostic agents for magnetic resonance and photoacoustic imaging. Hybrid nanoparticles of a conjugated polymer (PCPDTBT), a phospholipid (D8PE) with a primary amine polar head, and iron oxide (Fe3O4) nanoparticles were prepared by a phase-separated film shattering process by varying the iron oxide concentration while maintaining a fixed mixing ratio of PCPDTBT and D8PE. Notably, the hybrid nanoparticles assembled at a molar mixing ratio of 1:1:0.8 (PCPDTBT/D8PE/Fe3O4) exhibited the shortest transversal relaxation time, T2, and a photoacoustic signal 22 times higher than that obtained at the 1:1:0 mixing ratio. Structural analysis by X-ray diffraction together with the measurements of energy transfer by transient absorption spectroscopy confirmed that the structural ordering of these hybrid nanoparticles was responsible for their enhanced photoacoustic and magnetic properties.