Core-shell Magnetite Research Articles

Efficient Immobilization of heavy metals using newly synthesized magnetic nanoparticles and some bacteria in a multi-metal contaminated soil.

Simultaneous application of modified Fe3O4 with biological treatments in remediating multi-metal polluted soils, has rarely been investigated. Thus, a pioneering approach towards sustainable environmental remediation strategies is crucial. In this study, we aimed to improve the efficiency of Fe3O4 as adsorbents for heavy metals (HMs) by applying protective coatings. We synthesized core-shell magnetite nanoparticles coated with modified nanocellulose, nanohydrochar, and nanobiochar, and investigated their effectiveness in conjunction with bacteria (Pseudomonas putida and Bacillus megaterium) for remediating a multi-metal contamination soil. The results showed that the coatings significantly enhanced the immobilization of heavy metals in the soil, even at low doses (0.5%). The coating of nanocellulose had the highest efficiency in stabilizing metals due to the greater variety of surface functional groups and higher specific surface area (63.86 m2 g-1) than the other two coatings. Interestingly, uncoated Fe3O4 had lower performance (113.6 m2 g-1) due to their susceptibility to deformation and oxidation. The use of bacteria as a biological treatment led to an increase in the stabilization of metals in soil. In fact, Pseudomonas putida and Bacillus megaterium increased immobilization of HMs in soil successfully because of extracellular polymeric substances and intensive negative charges. Analysis of metal concentrations in plants revealed that Ni and Zn accumulated in the roots, while Pb and Cd were transferred from the roots to the shoots. Treatment Fe3O4 coated with modified nanocellulose at rates of 0.5 and 1% along with Pseudomonas putida showed the highest effect in stabilizing metals. Application of coated Fe3O4 for in-situ immobilization of HMs in contamination soils is recommendable due to their high metal stabilization efficiency and suitability to apply in large quantities.

Synthesis of Mesoporous Core Shell Magnetite Bioactive Glass Nanoparticles for Magnetic Hyperthermia Treatment of Cancer

AbstractMultiple biological advances have made use of bioactive glass (BG) nanoparticles (NPs) in regenerative medicine, bone and tooth repair, drug and gene transfer, cancer treatment, and cosmetics. Normal biocompatible coatings alongside hydrocarbons, polymers, and silica significantly affect fundamental attributes of NPs. In this study, we synthesized a novel mesoporous BG NPs with magnetite core shell (AMAG_BG) using L‐arginine as a template processing magnetic hyperthermia (MH). BG network coverage on magnetite (AMAG) NPs were orchestrated first time by bio‐inspired synthesis in watery dissolvable. AMAG and AMAG_BG NPs were characterized by utilizing FE‐SEM, HR‐TEM, and BET analysis. The elemental composition of L‐arginine templated magnetite (AMAG) and AMAG_BG NPs was also determined by XPS and EDX analysis. Characteristics of AMAG_BG were contrasted with bare AMAG NPs in morphology, particle size, porosity, and composition. The fabricated BG NPs′ in‐vitro bioactivity and heat studies were successfully monitored after interaction with simulated bodily fluid (SBF). Magnetic studies and in‐vitro heat studies together demonstrated the behavior of BG NPs towards MH treatment of cancerous cells. Cytotoxicity tests on AMAG_BG NPs using U2OS and human blood cells with appropriate control experiments revealed biocompatibility. The study represents magnetic and thermal property‐dependent sustainable synthetic process of AMAG BG NPs for cancer treatment.

An efficient magnetothermal actuation setup for fast heating/cooling cycles or long-term induction heating of different magnetic nanoparticle classes

Alternating magnetic fields (AMFs) in the ∼100 kHz frequency regime cause magnetic nanoparticles (MNPs) to dissipate heat to their nanoscale environment. This mechanism is beneficial for a variety of applications in biomedicine and nanotechnology, such as localized heating of cancer tissue, actuation of drug release, or inducing conformational changes of molecules. However, engineering electromagnetic resonant circuits which generate fields to efficiently heat MNPs over long time scales, remains a challenge. In addition, many applications require fast heating/cooling cycles over ΔT= 5 °C–10 °C to switch the sample between different states. Here, we present a home-built magnetothermal actuation setup maximized in its efficiency to deliver stable AMFs as well as to enable fast heating/cooling cycles of MNP samples. The setup satisfies various demands, such as an elaborate cooling system to control heating of the circuit components as well as of the sample due to inductive losses. Fast cycles of remote sample heating/cooling (up to ±15 °C min−1) as well as long-term induction heating were monitored via contact-free thermal image recording at sub-mm resolution. Next to characterizing the improved hyperthermia setup, we demonstrate its applicability to heat different types of MNPs: ‘nanoflower’-shaped multicore iron oxide nanoparticles, core shell magnetite MNPs, as well as magnetosomes from magnetotactic bacteria (Magnetospirillum gryphiswaldense). MNPs are directly compared in their structure, surface charge, magnetic properties as well as heating response. Our work provides practical guidelines for AMF engineering and the monitoring of MNP heating for biomedical or nano-/biotechnological applications.

Synergistic antibacterial activity of compact silver/magnetite core-shell nanoparticles core shell against Gram-negative foodborne pathogens.

The development of innovative antibacterial drugs against foodborne pathogens has led to an interest in novel materials such as nanomaterials. The unique features of nanomaterial qualify it for use as an antibacterial treatment. Noble metals and metal oxide nanoparticles, such as silver and magnetite nanoparticles, have been shown to be effective antibacterial medications against a range of microorganisms. In this work, Ag@Fe3O4 -NPs were fabricated by using a wet chemical reduction and modified co-precipitation techniques. The antibacterial efficiency of the Ag/Fe3O4 core shell nanoparticles was investigated by applying various techniques, such as the Kirby–Bauer Disk Diffusion test, minimum inhibitory concentration (MIC) and bactericidal concentration (MBC), Colony Forming Unit (CFU), and kill time assay. The toxicity mechanism of Ag@Fe3O4 -NPs against Salmonella typhimurium and Escherichia coli was studied by apoptosis and reactive oxygen species (ROS) assays. The data revealed that a cubic core was surrounded by a silver shell, which indicated the regular morphology of silver magnetite core shell nanoparticles without any aggregation. Furthermore, Ag@Fe3O4 -NPs is more toxic against S. typhimurium and E. coli than Ag-NPs and Fe3O4 NPs. The MIC values for Ag/Fe3O4 NPs against S. typhimurium and E. coli were 3.1 and 5.4 μg/ml, respectively, whereas the MIC values for Ag-NPs and MNPs against S. typhimurium and E. coli were 4.1 and 8.2 μg/ml for Ag-NPs and 6.9 and 10.3 μg/ml for MNPs. The results showed the ability of Ag@Fe3O4 -NPs to induce apoptosis by generating ROS. Also, the ability of Ag@Fe3O4 -NPs to liberate free Ag+ and generate ROS via the Haber-Weiss cycle may be a plausible mechanism to explain the toxicity of Ag@Fe3O4 -NPs - NPs.

Microwave-Assisted Sol-Gel Preparation of the Nanostructured Magnetic System for Solid-Phase Synthesis.

This work describes a new synthesis method for core–shell magnetite nanoparticles with a secondary silica shell, functionalized with a linker system (Fe3O4-PABA-SiO2-linker) using a microwave-assisted heating technique. The functionalized solid nanomaterial was used for the nanophase synthesis of peptides (Fmoc route) as a solid support. The co-precipitation method was selected to obtain magnetite nanoparticles and sol–gel technique for silica coating using a microwave-assisted (MW) procedure. The magnetic properties of the nanoparticle core offer the advantage of a quick and easy alternative for the magnetic separation of the product from the reaction mixture, facilitating all the intermediary washing and separation operations. The intermediate and final materials were analyzed by advanced characterization methods. The effectiveness of the nanophase peptide synthesis using this nanostructured material as solid support was demonstrated for a short peptide sequence.

Synthesis, characterization and adsorption capacity of lead(II) ions of Fe3O4/C core-shell structure materials

Core shell magnetite nanoparticles (Fe3O4@C) as adsorbent for lead ions from aqueous solution were synthesized. The characteristics of the modified materials were analysed. It could also be shown that the adsorption isotherms were well described by the Langmuir model. The kinetic of the adsorption process was found to follow the pseudo-second-order model expression. Thermodynamic studies indicated that the adsorption process was feasible, spontaneous and endothermic.

Selective aptamer conjugation to silver-coated magnetite nanoparticles for magnetic solid-phase extraction of trace amounts of Pb2+ ions.

Herein, a novel aptamer-functionalized magnetic adsorbent was developed and combined with magnetic solid-phase extraction (MSPE) for the specific enrichment of Pb2+ ions prior to flame atomic absorption spectrometric detection. First, silver-coated magnetite core–shell nanoparticles (Fe3O4@Ag MNPs) were synthesized by the chemical reduction of silver ions on the surface of magnetite nanoparticles. After that, the selective DNA aptamer against Pb2+ was conjugated on the surface of the synthesized nanoparticles to form aptamer-modified magnetic nanoparticles (Fe3O4@Ag-APT). The characterization of the prepared adsorbent was performed through SEM imaging, XRD, FT-IR, EDX, and DRS instruments. The influence of the various experimental parameters on the adsorption and desorption steps in MSPE was investigated via Taguchi experimental design to optimize different parameters. Under the optimized conditions, the Pb2+ calibration graph was linear in the range of 33–1000 μg L−1. The relative standard deviation (RSD%) of the method for six replicates containing 100 μg L−1 of Pb2+ ions was 0.34%. Furthermore, the limit of detection (LOD) and the limit of quantification (LOQ) were 10 μg L−1 and 33.3 μg L−1, respectively. Finally, the applicability of the proposed method was successfully confirmed by preconcentration and determination of trace amounts of Pb2+ ions in tap and seawater samples. We showed a proof of concept for Fe3O4@Ag-APT as an efficient bio-adsorbent, offering a promising strategy for the specific binding/removal of toxic heavy metal ions.

Synthesis and characterization of core-shell magnetite nanoparticles with modified nano-cellulose for removal of radioactive ions from aqueous solutions

Core-shell superparamagnetic magnetite nanoparticles material with nano-cellulose and modified nano-cellulose (as nano-cellulose citrate, nano-cellulose carbmate and nano-cellulose acrylamide graft) were synthesized using chemical method. The samples were characterized by Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Fourier Transformed Infrared Spectroscopy (FTIR) and Vibration Sample Magnetometer (VSM). Solid phase extraction (SPE) technique was used to extract the Th232 daughters from aqueous solution using samples. The extraction efficiencies of samples were investigated by measuring the activity of radioactive ions before and after treatment using High resolution gamma rays spectrometer of hyper pure germanium detector. The effects of type of sorbent, contact time, pH, initial concentrations of adsorbate, adsorption kinetics and adsorption isotherms in one average thickness shell were investigated. The present work study shows that the coating of nano-magnetite with modified nano-cellulose enhanced the adsorption process especially nano-cellulose citrate. Using modified nano-cellulose as coating for Fe3O4 gives economic feasibility, which is to be used in water treatment due to the low cost of production, zero toxicity and suitability to apply to a large volume of solution.

Competitive adsorption of methylene blue and Pb (II) ions on the nano-magnetic activated carbon and alumina

The adsorption of methylene blue (MB) in single and binary solutions were investigated on new promising functionalized magnetic wood based activated carbon (MFMWAC), peach stone activated carbon (MFMPAC) and alumina (MFMA) derived by a facile preparation method. Characterization of the magnetic nano-adsorbents was achieved by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), Vibrating sample magnetometer (VSM) and zeta potential tests. Findings revealed that the core-shell magnetite nanocomposites were formed with size of less than 50 nm. The kinetic and isotherm models were also analyzed for the adsorption of MB. Equilibrium adsorption was evaluated employing Langmuir and Freundlich equations, in which Freundlich model was in good agreement with the experimental results. Maximum adsorption capacities of MFMWAC, MFMPAC and MFMA were measured as 434.13, 437.78 and 196.08 mg/g for MB, respectively. The pseudo second order kinetic with higher correlation coefficient indicated a better fit with MB adsorption. Competitive adsorption of MB disclosed that the adsorption capacities of the carbonaceous adsorbents for MB reduced considerably by adding the Pb (II) ions to the aqueous solutions. However, the remarkable capacity of MB was calculated to be 175.39 and 182.45 mg/g by using the extended Langmuir for MFMWAC and MFMPAC, respectively in the binary solution. Reusability of the magnetic adsorbent was also investigated in the competitive adsorption for six cycles which showed that the prepared adsorbent can be used for the real applications.

Dual-channel biosensor for Hg2+ sensing in food using Au@Ag/graphene-upconversion nanohybrids as metal-enhanced fluorescence and SERS indicators

Here, we proposed a novel dual-channel biosensor for rapid and sensitive detection of Hg2+. Compared with the previous biosensors, the Au@Ag/graphene-upconversion (Au@Ag-GU) was prepared via a facile method and acted as a versatile signal indicator that can simultaneously readout surface-enhanced Raman spectroscopy (SERS) and fluorescence signals for Hg2+detection. In this strategy, the core shell magnetite colloid nanocrystal clusters-polymethacrylic acid magnetic beads (MCNCs/PMAA MBs) were synthesized and conjugated with aptamer to specific capture the Hg2+. The dual-channel biosensor was thus fabricated by immobilizing the Au@Ag-GU onto the surface of MBs through the complementary pairing of aptamer and complementary DNA (cDNA). Upon Hg2+ incubation, Hg2+ preferably bound to the MBs-aptamer, resulting in the subsequent release of preloaded cDNA-Au@Ag-GU into supernatants. Under magnetic attraction, the MBs-aptamer was accumulated immediately, resulting in the concentration of Hg2+ become homodromous proportional to the dual channel intensity of the supernatants. Under the optimized conditions, the dual channel biosensor achieved excellent performances for Hg2+ with limits of detection (LOD) of 0.33 and 1 ppb, respectively. Furthermore, the feasibility of the biosensor to qualify Hg2+was also established in spiked tap water and milk samples. This strategy may provide a bridge between a highly sensitive fluorescence assay and a rapid SERS assay, it can broaden the applicability of Hg2+ detection, which can be easy to detect Hg2+ in real samples by coupling with SERS or fluorescence assay.

Magnetic solid-phase extraction of sulfonamide antibiotics in water and animal-derived food samples using core-shell magnetite and molybdenum disulfide nanocomposite adsorbent

A molybdenum disulfide(MoS2)-based core-shell magnetic nanocomposite (Fe3O4@MoS2) was synthesized by the stepwise hydrothermal method. Two-dimension ultrathin MoS2 sheets with a thickness of approximately 20 nm were grown in situ on the surface of Fe3O4 (∼200 nm). They were employed as an adsorbent for the magnetic solid-phase extraction (MSPE) of sulfonamide antibiotics (SAs) from water samples. High-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) was used for SA quantitation. Extraction parameters, including the pH effect, amount of Fe3O4@MoS2, extraction time, temperature, and desorption conditions, were systematically investigated. The electrostatic interaction between the positively charged SAs and negatively charged MoS2 nanoparticles in the optimal extraction conditions enhanced the adsorption of SAs on the sorbent surface. Under chosen conditions, the proposed strategy achieved wide linear range of 1.0–1000 ng·L−1 SAs, low limits of detection (LOD, 0.20–1.15 ng·L−1, S/N = 3:1), good trueness (recoveries between 85.50–111.5%), satisfactory repeatability and reproducibility (relative standard deviation, <10%, n = 5), and excellent recoveries between 80.20% and 108.6% for SAs determination in spiked waste water samples. The proposed strategy was validated and successfully applied for the analysis of water, milk, pork meat and fish meat. The nanocomposites, which have the combined advantages of magnetic separation and high adsorption affinity toward SAs, are a promising sorbent for antibiotics extraction from real samples.

Bimetallic Nanoparticles Anchored on Core-Shell Support as an Easily Recoverable and Reusable Catalytic System for Efficient Nitroarene Reduction.

We report an easily recoverable and reusable versatile magnetic catalyst (Fe3O4@CS_AgNi, where CS = chitosan) for organic reduction reactions. The catalytic system is prepared by dispersing AgNi bimetallic nanoparticles on the magnetite core–shell (Fe3O4@CS). The as-synthesized catalyst has been characterized by spectroscopic techniques, such as IR, UV–vis, and X-ray photoelectron spectroscopy (XPS), and analytical tools, such as thermogravimetric analysis, powder X-ray diffraction, Brunauer–Emmett–Teller adsorption, FEG–scanning electron microscopy, high-resolution transmission electron microscopy (HR-TEM), inductively coupled plasma-atomic emission spectroscopy, and magnetic measurements. HR-TEM studies indicate the core–shell structure of Fe3O4@CS and confirm the presence of AgNi nanoparticles on the surface of Fe3O4@CS spheres. IR spectral and XPS studies lend evidence for the occurrence of a strong chemical interaction between the amino groups of CS and AgNi nanoparticles. The nano-catalyst Fe3O4@CS_AgNi rapidly reduces p-nitrophenol to p-aminophenol using NaBH4 as the reductant within a few minutes under ambient conditions (as monitored by UV–visible spectroscopy). The utility of this catalytic system has also been extended to the reduction of other nitroarenes. A strong interaction between Fe3O4@CS and AgNi nanoparticles impedes the leaching of AgNi nanoparticles from the core–shell support, leading to excellent reusability of the catalyst.

Iron Oxide Magnetie-Polyethylene Glycol-Layered Double Hydroxide Core Shell Nanoparticles for Drug Delivery

Recently, micro- and nanoparticles with magnetic core and functional shell structures have received much attention because of their potential applications in drug delivery, biosensors catalysis, selective separation and chromatography etc. Layered double hydroxides (LDHs) nanoparticles (NPs) are an efficient cellular delivery vehicle for many negatively charged chemical species. Recently, Mg and Zn/Al-layered double hydroxide (Mg/Al-LDH) and (Zn/Al-LDH) has emerged as a promising nanocarrier for drug delivery system due to its unique properties such as low cytotoxicity, pH-controlled release, good biocompatibility, tunable particle size, and protection of drugs in the interlayer. Various anionic biofunctional molecules, including DNA, SiRNA, drugs and vitamins have been successfully intercalated into LDH interlayers, protected from enzyme degradation and delivered into the cytoplasm in mammalian cells through the clathrin-mediated endocytosis pathway. In this study, a magnetite core shell nanodrug delivery formulation was designed based on Fe3O4-PEG-Zn/Al-LHDs or Mg/Al-LDHs loaded with anticancer drug 5-Fluoro-2,4(1H,3H)-pyrimidinedione commonly called 5-fluorouracil. Designed core shell magnetite nanoparticles formulation was characterized using XRD, zeta sizer and high performance liquid chromatography (HPLC).

Fabrication of Fe3O4/ZnO magnetite core shell and its application in photocatalysis using sunlight

Three chore-shell magnetite ZnO catalysts (Fe3O4/ZnO: M1, Fe3O4/SiO2/ZnO: M2, Fe3O4/SiO2-APTS/ZnO: M3) were prepared, characterized and tested for their photocatalysis in the degradation of methylene blue (MB) dye under sunlight irradiation. M2 and M3 catalysts exhibited better kinetics and higher activity. The silica coating of Fe3O4 in M2 and M3 catalysts enhanced efficient transport of MB dye to the ZnO site and thus enhanced photocatalysis. Photocatalytic reactivity was also related to the defects present in the samples under the synthesized conditions. Photoluminescence studies indicated the order of the defects in ZnO catalyst as M2>M3>M1. The presence of ZnO defects in the samples (M2 & M3) slowed electron recombination time, enhanced hydroxyl radical formation and hence performed faster degradation of MB. The significant enhancement in photoactivity could be attributed to the synergistic effect of adsorption by silica and ZnO catalysis. The recycle experiments using external magnetic showed the remained activity which demonstrated the stable and efficient magnetic separable catalysts.

Determining the size of nanoparticles in the example of magnetic iron oxide core-shell systems

The size of nanoparticles is one of the most important factors for their possible applications. Various techniques for the nanoparticle size characterization are available. In this paper selected techniques will be considered base on the prepared core-shell magnetite nanoparticles. Magnetite is one of the most investigated and developed magnetic material. It shows interesting magnetic properties which can be used for biomedical applications, such as drug delivery, hypothermia and also as a contrast agent. To reduce the toxic effects of Fe3O4, magnetic core was covered by dextran and gelatin. Moreover, the shell was doped by fluorescent dye for confocal microscopy investigation. The main investigation focused on the methods for particles size determination of modified magnetite nanoparticles prepared with different techniques. The size distribution were obtained by nanoparticle tracking analysis, dynamic light scattering and transmission electron microscopy. Furthermore, fluorescent correlation spectroscopy (FCS) and confocal microscopy were used to compare the results for particle size determination of core-shell systems.

Online stacking of carboxylated magnetite core-shell nanoparticles in capillary electrophoresis.

The stacking effect on carboxylated magnetite core-shell nanoparticles using sodium borate buffer pH 9.5 as the background electrolyte is presented. The ionic strength of the background electrolyte ranged from 5 to 100mM, and the ionic strength of a sample zone ranged from 5 to 100mM. Moreover, water was used as the sample dispersant. Both stacking and de-stacking effects were observed when conductivities of the sample zone and the background electrolyte differed. An explanation of carboxylated magnetic core-shell nanoparticles behavior was suggested based on the Derjaguin-Landau-Verwey-Overbeek theory supposing that the aggregation point is defined by the energetic barrier as the sum of energies given by electrostatic interactions and Van der Waals interactions. Moreover, the stacking conditions were applied for the evaluation of the lowest detectable dilution of magnetic nanoparticles. The carboxylated magnetic nanoparticles were dispersed in 10mM borate/NaOH pH 9.5 and injected for 60s to the background electrolyte composed of 100mM borate/NaOH pH 9.5 that allowed the detection of 100-fold diluted nanoparticles.

Refinement of Magnetite Nanoparticles by Coating with Organic Stabilizers.

Magnetite nanoparticles are of great importance in nanotechnology and nanomedicine and have found manifold applications. Here, the effect of coating of magnetite nanoparticles with organic stabilizers, such as O-phosphoryl ethanolamine, glycerol phosphate, phospho-l-ascorbic acid, phospho-d,l-serine, glycolic acid, lactic acid, d,l-malic acid, and d,l-mandelic acid was studied. Remarkably, this procedure led to an improvement of saturation magnetization in three cases rather than to an unfavorable decrease as usually observed. Detailed X-ray powder diffraction investigations revealed that changes in the average crystallite occurred in the coating process. Surprisingly, changes of the average crystallite sizes in either direction were further observed, when the exposure time to the stabilizer was increased. These results imply a new mechanism for the well-known coating of magnetite nanoparticles with stabilizers. Instead of the hitherto accepted simple anchoring of the stabilizers to the magnetite nanoparticle surfaces, a more complex recrystallization mechanism is likely, wherein partial re-dispersion of magnetite moieties from the nanoparticles and re-deposition are involved. The results can help producers and users of magnetite nanoparticles to obtain optimal results in the production of core shell magnetite nanoparticles.

The effect of polycarboxylate shell of magnetite nanoparticles on protein corona formation in blood plasma

The development of protein corona around nanoparticles upon administration to the human body is responsible in a large part for their biodistribution, cell-internalization and toxicity or biocompatibility. We studied the influence of the chemical composition of polyelectrolyte shells (citric acid (CA) and poly(acrylic-co-maleic acid) (PAM)) of core-shell magnetite nanoparticles (MNPs) on the evolution of protein corona in human plasma (HP). The aggregation state and zeta potential of the particles were measured in the range of HP concentration between 1 and 80 (v/v)% 3min and 20h after dispersing the particles in HP diluted with Tris buffered saline. Naked MNPs aggregated in HP solution, but the carboxylated MNPs became stabilized colloidally at higher plasma concentrations. Significant differences were observed at low plasma concentration. CA@MNPs aggregated instantly while the hydrodynamic diameter of PAM@MNP increased only slightly at 1–3v/v % HP concentrations. The observed differences in protein corona formation can be explained by the differences in the steric effects of the polycarboxylate shells. It is interesting that relatively small but systematic changes in zeta potential alter the aggregation state significantly.

Magnetite Core–Shell Nanoparticles in Nondestructive Flaw Detection of Polymeric Materials

Nondestructive flaw detection in polymeric materials is important but difficult to achieve. In this research, the application of magnetite nanoparticles (MNPs) in nondestructive flaw detection is studied and realized, to the best of our knowledge, for the first time. Superparamagnetic and highly magnetic (up to 63 emu/g) magnetite core-shell nanoparticles are prepared by grafting bromo-end-group-functionalized poly(glycidyl methacrylate) (Br-PGMA) onto surface-modified Fe3O4 NPs. These Fe3O4-PGMA NPs are blended into bisphenol A diglycidylether (BADGE)-based epoxy to form homogeneously distributed magnetic epoxy nanocomposites (MENCs) after curing. The core Fe3O4 of the Fe3O4-PGMA NPs endows the MENCs with magnetic property, which is crucial for nondestructive flaw detection of the materials, while the shell PGMA promotes colloidal stability and prevents NP aggregation during curing. The eddy current testing (ET) technique is first applied to detect flaws in the MENCs. Through the brightness contrast of the ET image, surficial and subsurficial flaws in MENCs can be detected, even for MENCs with low content of Fe3O4-PGMA NPs (1 wt %). The incorporation of Fe3O4-PGMA NPs can be easily extended to other polymer and polymer-based composite systems and opens a new and very promising pathway toward MNP-based nondestructive flaw detection in polymeric materials.

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.