Magnetite Nanoclusters Research Articles

Engineering Magnetic Nanoclusters for Highly Efficient Heating in Radio-Frequency Nanowarming.

Effective thawing of cryopreserved samples requires rapid and uniform heating. This is achievable through nanowarming, an approach that heats magnetic nanoparticles by using alternating magnetic fields. Here we demonstrate the synthesis and surface modification of magnetic nanoclusters for efficient nanowarming. Magnetite (Fe3O4) nanoclusters with an optimal diameter of 58 nm exhibit a high specific absorption rate of 1499 W/g Fe under an alternating magnetic field at 43 kA/m and 413 kHz, more than twice that of commercial iron oxide cores used in prior nanowarming studies. Surface modification with a permeable resorcinol-formaldehyde resin (RFR) polymer layer significantly enhances their colloidal stability in complex cryoprotective solutions, while maintaining their excellent heating capacity. The Fe3O4@RFR nanoparticles achieved a high average heating rate of 175 °C/min in cryopreserved samples at a concentration of 10 mg Fe/mL and were successfully applied in nanowarming porcine iliac arteries, highlighting their potential for enhancing the efficacy of cryopreservation.

Magnetic heating properties of magnetite nanoclusters produced by precipitation

Magnetic heating properties of magnetite nanoclusters produced by precipitation

Polyphenol‐Mediated Synthesis of Superparamagnetic Magnetite Nanoclusters for Highly Stable Magnetically Responsive Photonic Crystals

AbstractAchieving high stability and excellent optical performance in complex environments is crucial for practical applications of magnetically responsive photonic crystals (MRPCs). It, however, remains a great challenge. This study demonstrates a polyphenol‐mediated strategy for synthesizing size‐controllable superparamagnetic magnetite (Fe3O4) colloid nanocrystal clusters (CNCs) that can be stably dispersed in various polar solvents to form MRPCs with brilliant structural colors for a long term. As tannic acid (TA) functions as a linker to robustly bind polyvinylpyrrolidone (PVP) chains to Fe3O4 surfaces, the MRPCs can maintain nearly constant diffraction wavelength and high reflectance for up to 4 years. The strong coordination between TA and Fe3+ inhibits crystal growth, ensuring the small primary crystal size and superparamagnetism of Fe3O4@TA‐PVP CNCs. Partial oxidation of TA accelerates the crystal nucleation and growth, reducing the overall CNC particle size, which can be utilized for controlling the particle size. Additionally, enhancing the dissolution of PVP before the solvothermal reaction improves the size monodispersity of the products, making the as‐constructed MRPCs ideal for practical applications in color display, sensors, anti‐counterfeiting, and camouflage. The Fe3O4@TA‐PVP CNCs with high stability and versatility for surface‐functionalization are also promising for magnetic resonance imaging, targeting drug delivery, recyclable catalysis, and magnetic nanomotors.

Carbon-coated magnetite nanoclusters with NIR-II absorbance for imaging-guided photothermal-chemodynamic synergistic therapy

Carbon-coated magnetite nanoclusters with NIR-II absorbance for imaging-guided photothermal-chemodynamic synergistic therapy

Magnetic Nanoclusters Stabilized with Poly[3,4-Dihydroxybenzhydrazide] as Efficient Therapeutic Agents for Cancer Cells Destruction.

Magnetic structures exhibiting large magnetic moments are sought after in theranostic approaches that combine magnetic hyperthermia treatment (MH) and diagnostic magnetic resonance imaging in oncology, since they offer an enhanced magnetic response to an external magnetic field. We report on the synthesized production of a core-shell magnetic structure using two types of magnetite nanoclusters (MNC) based on a magnetite core and polymer shell. This was achieved through an in situ solvothermal process, using, for the first time, 3,4-dihydroxybenzhydrazide (DHBH) and poly[3,4-dihydroxybenzhydrazide] (PDHBH) as stabilizers. Transmission electron microscopy (TEM) analysis showed the formation of spherical MNC, X-ray photoelectronic spectroscopy (XPS) and Fourier transformed infrared (FT-IR) analysis proved the existence of the polymer shell. Magnetization measurement showed saturation magnetization values of 50 emu/g for PDHBH@MNC and 60 emu/g for DHBH@MNC with very low coercive field and remanence, indicating that the MNC are in a superparamagnetic state at room temperature and are thus suitable for biomedical applications. MNCs were investigated in vitro, on human normal (dermal fibroblasts-BJ) and tumor (colon adenocarcinoma-CACO2, and melanoma-A375) cell lines, in view of toxicity, antitumor effectiveness and selectivity upon magnetic hyperthermia. MNCs exhibited good biocompatibility and were internalized by all cell lines (TEM), with minimal ultrastructural changes. By means of flowcytometry apoptosis detection, fluorimetry, spectrophotometry for mitochondrial membrane potential, oxidative stress, ELISA-caspases, and Western blot-p53 pathway, we show that MH efficiently induced apoptosis mostly via the membrane pathway and to a lower extent by the mitochondrial pathway, the latter mainly observed in melanoma. Contrarily, the apoptosis rate was above the toxicity limit in fibroblasts. Due to its coating, PDHBH@MNC showed selective antitumor efficacy and can be further used in theranostics since the PDHBH polymer provides multiple reaction sites for the attachment of therapeutic molecules.

Magnetite–reduced graphene oxide nanocomposite as an efficient heterogeneous Fenton catalyst for the degradation of tetracycline antibiotics

Effective Fenton degradation of tetracycline over magnetite nanoclusters supported on reduced graphene oxide was observed.

NIR-II Responsive Hollow Magnetite Nanoclusters for Targeted Magnetic Resonance Imaging-Guided Photothermal/Chemo-Therapy and Chemodynamic Therapy.

Phototherapy in the second near-IR (1000-1700nm, NIR-II) window has achieved much progress because of its high efficiency and relatively minor side effects. In this paper, a new NIR-II responsive hollow magnetite nanocluster (HMNC) for targeted and imaging-guided cancer therapy is reported. The HMNC not only provides a hollow cavity for drug loading but also serves as a contrast agent for tumor-targeted magnetic resonance imaging. The acid-induced dissolution of the HMNCs can trigger a pH-responsive drug release for chemotherapy and catalyze the hydroxyl radical (·OH) formation from the decomposition of hydrogen peroxide for chemodynamic therapy. Moreover, the HMNCs can adsorb and convert NIR-II light into local heat (photothermal conversion efficacy: 36.3%), which can accelerate drug release and enhance the synergistic effect of chemo-photothermal therapy. The HMNCs show great potential as a versatile nanoplatform for targeted imaging-guided trimodal cancer therapy.

Effect of surface functionalization on the heating efficiency of magnetite nanoclusters for hyperthermia application

Here we report the effect of surface functionalization on Fe3O4 assembled nanoclusters with biopolymers, like chitosan and dextran using the solvo-thermal route. XRD analyses confirmed the formation of cubic spinel structure with crystallite sizes ranging from 11 to 14 nm. HRTEM analyses revealed the formation of spherical nanoclusters. Magnetic measurements demonstrate the typical ferromagnetic behavior with saturation magnetization (Ms) up to 71.048, 69.829 and 68.228 Am2Kg−1 for Fe3O4 (FO), chitosan coated Fe3O4 (CFO) and dextran coated Fe3O4 (DFO) respectively at room temperature. Negligible coercivity (Hc) and remenance (Mr) at room temperature implies nearly superparamagnetic behavior. Field cooled (FC) and Zero field cooled (ZFC) measurements of magnetization at an applied field of 100 Oe resulting in the blocking temperature above room temperature for all the samples. Induction heating ability of the samples under alternating magnetic field were studied by means of specific absorption rate measurements (SAR). It is shown that the surface functionalization significantly enhanced the SAR value up to 40% i.e., from 144.08 W/g for FO to 233.28 W/g for DFO at 1 mg/ml concentration. The study also concluded that the dipolar interactions are solely responsible for self-heating behavior of the nanoparticles. It was observed that by changing the sample concentration and different coatings, the final temperature can be tuned to the intended therapeutic (hyperthermia) temperature range (40–44 °C). The in vitro cytocompatibility test resulted in cell viability of more than 90%, which proved that the prepared nanomaterials are promising for the hyperthermia applications.

Mesoporous Magnetite Nanoclusters as Efficient Nanocarriers for Paclitaxel Delivery

AbstractThis manuscript report the facile and cost‐effective fabrication of a targeted drug delivery system based on mesoporous magnetite (Fe3O4) nanoclusters. A simple one‐pot solvothermal method was followed for the synthesis of mesoporous Fe3O4 nanoclusters having average cluster size of ∼120 nm. As‐synthesized Fe3O4 nanoclusters exhibited excellent water dispersibility and superparamagnetism in conjunction with fast magnetic responsiveness. The anticancer drug, paclitaxel (PTX) was used as the model drug to investigate the applicability of as‐prepared mesoporous Fe3O4 nanoclusters for drug delivery applications. Successful loading of PTX into Fe3O4 nanoclusters was confirmed by Fourier‐transform infrared (FT‐IR) spectroscopy and drug loading capacity was estimated by thermogravimetric analysis (TGA). An efficient loading capacity of 17 % was achieved for PTX in the present study. The in vitro release of PTX was higher in acidic pH compared to physiological pH. As the extracellular pH of cancer cells is more acidic than that of normal cells, mesoporous Fe3O4 nanocluster‐based drug delivery vehicles can reduce the undesired release of PTX in blood circulation during the delivery process (at physiological pH) and can enhance the drug release inside the tumour cells. The results demonstrate that Fe3O4 nanoclusters developed in the present study are potential drug delivery systems

Water dispersible magnetite nanocluster coated with thermo‐responsive thiolactone‐containing copolymer

This work focused on surface modification of magnetite nanoparticle (MNP) with poly(poly(ethylene glycol) monomethyl ether methacylate)‐b‐(poly(N‐isopropylacrylamide)‐st‐poly(thiolactone acrylamide)), PPEGMA‐b‐(PNIPAAm‐st‐PTlaAm), diblock copolymer, synthesized via reversible addition‐fragmentation chain transfer (RAFT) polymerization to obtain the particles having good water dispersible PPEGMA brushes, thermo‐responsive PNIPAAm, and reactive thiolactone groups of PTlaAm. The thiolactone moiety in the copolymer can readily react with amino groups grafted on MNP surface and essentially induced the formation of MNP nanocluster. According to transmission electron microscopy (TEM), the size of the nanocluster ranged between 200 and 500 nm per cluster with 8 to 10 nm in diameter for each particle. Hydrodynamic diameter of the nanocluster significantly decreased as the dispersion temperature increased from 25°C to 45°C due to the shrinkage of thermo‐responsive PNIPAAm when crossing its lower critical solution temperature (LCST). This stable nanocluster might be potentially used as a magnetic carrier for control release of entrapped entities with a thermally triggering mechanism.

From high colloidal stability ferrofluids to magnetorheological fluids: tuning the flow behavior by magnetite nanoclusters

The flow behavior of practically structureless ferrofluids was tuned over a large range by adding well-defined amounts of magnetite nanoparticle clusters. Magnetite nanoparticle clusters with hydrophobic coating were dispersed in high colloidal stability transformer oil based ferrofluid samples, initially free of clusters. The resulting ferrofluid composition consists both of single (approx. 7 nm mean size) and clustered (280 nm average size) magnetite nanoparticles, each of them in a prescribed amount. This new approach allows a precise evaluation of the role of clusters on the ferrofluid flow behavior. The magnetite nanoparticle clusters obtained by a solvothermal method have a saturation magnetization of 75 emu g−1 and a remnant magnetization of 0.2 emu g−1 due to the large size (∼25 nm) of the magnetite nanoparticles in their composition. Long bundles of thin elongated needle like aggregates of magnetic nanocluster particles are formed in a magnetic field and produce a significant magnetorheological response of the bidisperse magnetic suspensions observed already for moderate applied magnetic field values. The dynamic yield stress and magnetoviscous effect are analyzed and compared with previous results concerning suspensions of micrometer size iron particles in a ferrofluid carrier. The viscoelastic properties and the interactions between the components of ferrofluid based magnetite nanoparticle cluster suspensions were evaluated by creep tests in zero and non-zero applied magnetic field. The bidisperse magnetic nanocomposite suspensions investigated provide a promising new formulation of MR fluids with improved kinetic stability to be used in seismic dampers and flow control devices.

Size-controlled synthesis of superparamagnetic magnetite nanoclusters for heat generation in an alternating magnetic field

We report the size-controlled synthesis of monodisperse magnetite (Fe3O4) nanoclusters by a facile and economic solvothermal route by using polyacrylic acid (PAA) as the coordinative ligand. In comparison with previous reports, nanocluster sizes were tuned over a broad range of 640–250 nm while retaining the superparamagnetic behaviour in the present study. The nanocluster sizes are varied by changing the amounts of PAA as well as water added in the reaction medium during the solvothermal treatment. As-synthesized Fe3O4 nanoclusters are characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The radio frequency alternating magnetic field induced heating studies indicate that the as-synthesized Fe3O4 nanoclusters are promising candidates for magnetic fluid hyperthermia applications. In the case of magnetic nanoclusters, consisting of individual superparamagnetic nanocrystals, the field induced heating occurs at two different length scale, viz. Neel-Brown relaxation of the individual superparamagnetic nanocrystals (length scale <10 nm) and Brownian relaxation of the entire nanoclusters (length scale ~250 nm or higher). Experimental findings indicate that the heating efficiency of the magnetic nanoclusters vary significantly with variations in the relaxation time at both length scales. The heating efficiency of the magnetic nanoclusters is also found to increase linearly with the square of the external field amplitudes, in accordance with the linear response theory.

Anisotropic magnetite nanoclusters with enhanced magnetization as an efficient ferrofluid in mass transfer and liquid hyperthermia

A stable dispersion of anisotropic superparamagnetic nanoparticles was introduced for efficient heat build-up and mass transfer under an external magnetic field.

Synthesis of Iron Oxide Nanoclusters by Thermal Decomposition.

Herein, we report a novel one-step solvothermal synthesis of magnetite nanoclusters (MNCs). In this report, we discuss the synthesis, structure, and properties of MNCs and contrast enhancement in T2-weighted MR images using magnetite nanoclusters. The effect of different organic acids, used as surfactants, on the size and shape of MNCs was investigated. The structure and properties of samples were determined by magnetic measurements, TGA, TEM, HRTEM, XRD, FTIR, and MRI. Magnetic measurements show that obtained MNCs have relatively high saturation magnetization values (65.1-81.5 emu/g) and dependence of the coercive force on the average size of MNCs was established. MNCs were transferred into an aqueous medium by Pluronic F-127, and T2-relaxivity values were determined. T2-Weighted MR phantom images clearly demonstrated that such magnetite nanoclusters can be used as contrast agents for MRI.

Graphene oxide-wrapped magnetite nanoclusters: A recyclable functional hybrid for fast and highly efficient removal of organic dyes from wastewater

We report the facile and cost-effective fabrication of a novel functional hybrid composed of graphene oxide (GO)-wrapped magnetite (Fe3O4) nanoclusters (Fe3O4@GO) by electrostatically driven co-assembly. In comparison with previously reported Fe3O4-GO composites that were prepared through one-pot, in situ deposition of smaller-sized Fe3O4 nanoparticles, the Fe3O4@GO hybrid composite reported in the present study are obtained by weak electrostatic interaction between negatively charged GO nanosheets and positively charged Fe3O4 nanoclusters (size ∼500 nm). The as-prepared Fe3O4@GO hybrid has a core-shell structure where thin and flexible GO shells efficiently infold the Fe3O4 nanocluster core. The adsorptive characteristics of Fe3O4@GO hybrid was evaluated using two model cationic dyes; methylene blue (MB) and rhodamine B (RhB) and one model anionic dye; methyl orange (MO). The adsorption of dyes onto Fe3O4@GO hybrid composite was investigated as a function of solution pH, adsorbent dosage, ionic strength, contact time and temperature. The adsorption kinetics, isotherms, thermodynamics, stability, and reusability of the adsorbent were also studied in detail. The results showed that the adsorption kinetics and the equilibrium adsorptions are well-fitted with pseudo-second order kinetic model and Langmuir isotherm model, respectively. The maximum adsorption capacities for MB, RhB and MO are 131.10, 34.50 and 39.95 mg/g respectively at 303 K. The Fe3O4@GO adsorbent exhibited rapid magnetic separation, easy regeneration, excellent stability, and good sustainability in removal efficiency even after continued recycling. The results demonstrated that Fe3O4@GO composite possesses great potential as an efficient and recyclable adsorbent for the removal of both cationic and anionic dye pollutants in environmental remediation.

Novel Nanofluids Based on Magnetite Nanoclusters and Investigation on Their Cluster Size-Dependent Thermal Conductivity

To probe the effect of particle size on thermal conductivity (k) enhancement in nanofluids, especially in a very large particle size range, we study the cluster size-dependent k in novel nanofluids containing magnetite (Fe3O4) nanoclusters. The Fe3O4 nanoclusters in the size range of 115 to 530 nm were synthesized by a facile and cost-effective solvothermal approach. The structural, surface, and magnetic characteristics of Fe3O4 nanoclusters were investigated by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and vibrating sample magnetometer (VSM). Thermal conductivity studies in diethylene glycol (DEG)-based Fe3O4 cluster nanofluids showed an enhancement in k with an increase in nanocluster size. With a fixed volume fraction (ϕ) = 0.0193, the k enhancement was about 5.3% and 12.6%, respectively, for nanofluids having cluster size of 115 and 530 nm. The observed increase in nanofluid k with increase...

Reusable magnetic nanocluster coated with poly(acrylic acid) and its adsorption with an antibody and an antigen

ABSTRACTThe synthesis of negatively charged magnetite nanoclusters grafted with poly(acrylic acid) (PAA) and their application as reusable nanosupports for adsorption with antibodies and antigens are presented in this article. They were facilely prepared via the free‐radical polymerization of PAA in the presence of functionalized magnetite nanoparticles to obtain highly negative charged nanoclusters with a high magnetic responsiveness and good dispersibility and stability in water. According to transmission electron microscopy, the sizes of the nanoclusters ranged between 200 and 500 nm, without large aggregation visually observed in water. The hydrodynamic size of the nanocluster consistently increased with increasing pH of the dispersion; this indicated its pH‐responsive properties, which was due to the repulsion of the anionic carboxylate groups in the structure. This nanocluster was successfully used as an efficient and reusable support for adsorption with anti–horseradish peroxidase antibody. It preserved higher than a 97% adsorption ability of the antibody after eight reuse cycles; this signified the potential of this novel nanocluster as a reusable support in the magnetic separation applications of other bioentities. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46160.

In-situ synthesis of carbon nanotubes decorated by magnetite nanoclusters and their applications as highly efficient and enhanced microwave absorber

We report a facile, in-situ polyol approach for the fabrication of magnetite/multi-wall carbon nanotubes (Fe3O4/MWCNTs) hybrids as highly efficient microwave absorber. SEM, TEM and XPS technologies indicate that uniform Fe3O4 nanoclusters were chemically bonded and anchored on the surface of MWCNTs without aggregation. ESR result suggests that the dipolar interactions of magnetic Fe3O4 nanoclusters were enhanced in the Fe3O4/MWCNTs hybrids. Combining the synergistic benefits of magnetic Fe3O4 nanoclusters and electric lightweight MWCNTs, the Fe3O4/MWCNTs hybrids perform highly improved microwave absorption properties in comparison with pure Fe3O4 nanoclusters and MWCNTs. For Fe3O4/MWCNTs hybrids, the strongest reflection loss (RL) values can reach −60.7dB at 11GHz with a matching thickness of only 1.8mm, and the effective microwave absorption bandwidth (RL>−10dB) ranges from 3.0GHz to 15.6GHz when the thickness is 1.5–5.0mm. Whereas, the RL value for the pure Fe3O4 nanoclusters and MWCNTs cannot reach −10dB in the whole measured frequency. These results suggest that the synergistic effect of the Fe3O4/MWCNTs hybrids has a great influence on the extremely enhanced microwave absorption properties. Taking the advantages of lightweight, antioxidation, high-efficient, easy preparation and low-cost, the Fe3O4/MWCNTs hybrids is believed to be a good candidate for microwave absorption, especially in the X-band (8–12GHz).

Luteinizing Hormone Releasing Hormone-Targeted Cisplatin-Loaded Magnetite Nanoclusters for Simultaneous MR Imaging and Chemotherapy of Ovarian Cancer.

Given the superior soft tissue contrasts obtained by MRI and the long residence times of magnetic nanoparticles (MNPs) in soft tissues, MNP-based theranostic systems are being developed for simultaneous imaging and treatment. However, development of such theranostic nanoformulations presents significant challenges of balancing the therapeutic and diagnostic functionalities in order to achieve optimum effect from both. Here we developed a simple theranostic nanoformulation based on magnetic nanoclusters (MNCs) stabilized by a bisphosphonate-modified poly(glutamic acid)-b-(ethylene glycol) block copolymer and complexed with cisplatin. The MNCs were decorated with luteinizing hormone releasing hormone (LHRH) to target LHRH receptors (LHRHr) overexpressed in ovarian cancer cells. The targeted MNCs significantly improved the uptake of the drug in cancer cells and decreased its IC50 compared to the nontargeted formulations. Also, the enhanced LHRHr-mediated uptake of the targeted MNCs resulted in enhancement in the T2-weighted negative contrast in cellular phantom gels. Taken together, the LHRH-conjugated MNCs show good potential as ovarian cancer theranostics.

Magnetite nanocluster@poly(dopamine)-PEG@ indocyanine green nanobead with magnetic field-targeting enhanced MR imaging and photothermal therapy in vivo

Multifunctional nanomaterials with the magnetic resonance imaging (MRI) guided tumor photothermal ablation ability have been extensively applied in biomedical research as one of the most exciting and challenging strategies for cancer treatment. Nevertheless, most of these nanomaterials still suffer from low accumulation in tumor tissues and insufficient photothermal ablation of tumors so far. Here, we report a novel approach to overcome these limitations using a core-shell magnetite nanocluster@poly(dopamine)-PEG@ICG nanobead compositing of magnetite nanocluster core with coating of poly(dopamine), then further conjugating with polyethylene glycol (PEG) and adsorbing indocyanine green (ICG) on the surface. The adsorbed ICG in the nanobead displays a higher photostability and photothermal conversion ability than free ICG, as well as additional photothermal effect rather than magnetite nanocluster and poly(dopamine), which endow the nanobead with enhanced photothermal killing efficiency against cancer cells under near-infrared (NIR) laser irritation. Furthermore, it is proved that these nanobeads have excellent biocompatibility, T2-weighted MR imaging and magnetic field targeting ability. By applying an external magnetic field (MF) focused on the targeted tumor, a magnetic targeting mediated enhanced accumulation is observed at tumor site as proved by a darker T2-weighted MR image. Utilizing the magnetic targeting strategy, enhanced photothermal tumor ablation was achieved under laser irradiation in vivo, which is reflected by the degree of tumor tissue damage and tumor growth delay. Therefore, this nanobead integrates the abilities of magnetic field-targeting, MR imaging and photothermal cancer therapy, and might be a promising theranostic platform for tumor treatment.