Influence of magnetite nanoparticles surface dissolution, stabilization and functionalization by malonic acid on the catalytic activity, magnetic and electrical properties

Characterization and antitumor effect of doxorubicin-loaded Fe3O4-Au nanocomposite synthesized by electron beam evaporation for magnetic nanotheranostics

Magnetic nanocomposites (MNC) are promising theranostic platforms with tunable physicochemical properties allowing for remote drug delivery and multimodal imaging. Here, we developed doxorubicin-loaded Fe3O4-Au MNC (DOX-MNC) using electron beam physical vapor deposition (EB-PVD) in combination with magneto-mechanochemical synthesis to assess their antitumor effect on Walker-256 carcinosarcoma under the influence of a constant magnetic (CMF) and electromagnetic field (EMF) by comparing tumor growth kinetics, magnetic resonance imaging (MRI) scans and electron spin resonance (ESR) spectra. Transmission (TEM) and scanning electron microscopy (SEM) confirmed the formation of spherical magnetite nanoparticles with a discontinuous gold coating that did not significantly affect the ferromagnetic properties of MNC, as measured by vibrating-sample magnetometry (VSM). Tumor-bearing animals were divided into the control (no treatment), conventional doxorubicin (DOX), DOX-MNC and DOX-MNC + CMF + EMF groups. DOX-MNC + CMF + EMF resulted in 14% and 16% inhibition of tumor growth kinetics as compared with DOX and DOX-MNC, respectively. MRI visualization showed more substantial tumor necrotic changes after the combined treatment. Quantitative analysis of T2-weighted (T2W) images revealed the lowest value of skewness and a significant increase in tumor intensity in response to DOX-MNC + CMF + EMF as compared with the control (1.4 times), DOX (1.6 times) and DOX-MNC (1.8 times) groups. In addition, the lowest level of nitric oxide determined by ESR was found in DOX-MNC + CMF + EMF tumors, which was close to that of the muscle tissue in the contralateral limb. We propose that the reason for the relationship between the observed changes in MRI and ESR is the hyperfine interaction of nuclear and electron spins in mitochondria, as a source of free radical production. Therefore, these results point to the use of EB-PVD and magneto-mechanochemically synthesized Fe3O4-Au MNC loaded with DOX as a potential candidate for cancer magnetic nanotheranostic applications.

Mössbauer and X-ray Diffraction Spectroscopy of High-Iron Bauxites from Kazakhstan

The bauxite ores of Kazakhstan were analyzed using Mössbauer spectroscopy, X-ray diffraction and an X-ray fluorescence analysis. Experimental data on the structural-phase composition of bauxites were obtained, and the features of the iron-bearing minerals within them were revealed. The studied bauxites were high in iron. The magnetic part of bauxite was mainly represented by aluminohematite with a concentration of CAl = 3.34-5.73 at.%, alongside goethite in small amounts. The predominant phase in the bauxite samples was the alumina-bearing mineral gibbsite with a well-crystallized monoclinic lattice. The main siliceous mineral of bauxite is kaolinite, which showed distorted octahedral positions in a number of samples. Siderite amounts were found to vary in the range of 0-15 at.% in the present iron-bearing minerals. Ilmenite was also present in the bauxite of some deposits; anatase was found in all bauxites and was the final product of ilmenite decomposition in the weathering crust.

An Overview of the Production of Magnetic Core-Shell Nanoparticles and Their Biomedical Applications

Several developments have recently emerged for core-shell magnetic nanomaterials, indicating that they are suitable materials for biomedical applications. Their usage in hyperthermia and drug delivery applications has escalated since the use of shell materials and has several beneficial effects for the treatment in question. The shell can protect the magnetic core from oxidation and provide biocompatibility for many materials. Yet, the synthesis of the core-shell materials is a multifaceted challenge as it involves several steps and parallel processes. Although reviews on magnetic core-shell nanoparticles exist, there is a lack of literature that compares the size and shape of magnetic core-shell nanomaterials synthesized via various methods. Therefore, this review outlines the primary synthetic routes for magnetic core-shell nanoparticles, along with the recent advances in magnetic core-shell nanomaterials. As core-shell nanoparticles have been proposed among others as therapeutic nanocarriers, their potential applications in hyperthermia drug delivery are discussed.

Mechanistic Insights into the Thermal Decomposition of Ammonium Perchlorate: The Role of Amino-Functionalized Magnetic Nanoparticles

This work reports the characterization and application of two promising nanocatalysts for the thermal decomposition of ammonium perchlorate (AP). To obtain these composite materials, magnetite nanoparticles (Fe₃O₄ NP_s) were functionalized with two different amine derivative groups, tertiary amine (Fe₃O₄ NP_s-A1) and quaternary amine. X-ray photoelectron spectroscopy and differential scanning calorimetry provided mechanistic insights into the thermal decomposition of AP. Furthermore, tertiary and quaternary amine groups play a critical role, where the presence of an extra proton could favor an electron-proton transfer as the rate-determining step. Moreover, Fe₃O₄ NP_s-A1 causes a diminution of the high-temperature decomposition of AP positively to 335 °C, increasing the energy release by 278 J g^-1 and consequently affording the lowest activation energy (102 kJ mol^-1), indicating a low degree of thermal stability, and accelerating the thermal decomposition of AP.

A New Design for Magnetic Poly(vinyl pivalate) for Biomedical Applications: Synthesis, Characterization, and Evaluation of Cytotoxicity in Fibroblasts, Keratinocytes, and Human Melanoma Cells

Polymers containing magnetic properties play an important role in biomedical therapies, such as embolotherapy or hyperthermia, for their differentiated properties. In this work, magnetite (Fe3O4) nanoparticles were synthesized by the coprecipitation method and dispersed into a thermoplastic matrix of poly(vinyl pivalate) through an emulsion polymerization process. The main goal was the individual encapsulation of magnetite nanoparticles to improve the magnetic response of the magneto-polymeric materials using polymerizable carboxylic acids as coating agents, minimizing the leaching of nanoparticles throughout the nanocomposite formation. For this purpose, synthesized magnetite had its surface modified by acrylic acid or methacrylic acid to improve its individual encapsulation during the polymerization step, thus generating a series of magnetic nanocomposite materials containing different amounts of magnetite intended for biomedical applications. X-ray diffractometry and TEM measurements provided a mean size of approximately 8 nm for the pure magnetite nanoparticles and a spherical morphology. Acid-functionalized Fe3O4 had a size of approximately 6 nm, while the nanocomposites showed a size of approximately 7 nm. Magnetization measurement provided a saturation magnetization value of approximately 75 emu/g and confirmed superparamagnetic behavior at room temperature. DSC analysis showed a glass transition temperature of 65 °C for poly(vinyl pivalate)-based nanocomposites. The tests realized with homopolymer and magnetic composites against different cell lineages (i.e., fibroblasts, keratinocytes, and human melanoma) to evaluate the levels of cytotoxicity showed good results in the different exposure times and concentrations used, since the obtained results showed cell viability greater than 70% compared to the control group, suggesting that the synthesized materials are very promising for medical applications.

Influence of Magnetite Nanoparticles Shape and Spontaneous Surface Oxidation on the Electron Transport Mechanism

The spontaneous oxidation of a magnetite surface and shape design are major aspects of synthesizing various nanostructures with unique magnetic and electrical properties, catalytic activity, and biocompatibility. In this article, the roles of different organic modifiers on the shape and formation of an oxidized layer composed of maghemite were discussed and described in the context of magnetic and electrical properties. It was confirmed that Fe3O4 nanoparticles synthesized in the presence of triphenylphosphine could be characterized by cuboidal shape, a relatively low average particle size (9.6 ± 2.0 nm), and high saturation magnetization equal to 55.2 emu/g. Furthermore, it has been confirmed that low-frequency conductivity and dielectric properties are related to surface disordering and oxidation. The electric energy storage possibility increased for nanoparticles with a disordered and oxidized surface, whereas the dielectric losses in these particles were strongly related to their size. The cuboidal magnetite nanoparticles synthesized in the presence of triphenylphosphine had an ultrahigh electrical conductivity (1.02 × 10-4 S/cm at 10 Hz) in comparison to the spherical ones. At higher temperatures, the maghemite content altered the behavior of electrons. The electrical conductivity can be described by correlated barrier hopping or overlapping large polaron tunneling. Interestingly, the activation energies of electrons transport by the surface were similar for all the analyzed nanoparticles in low- and high-temperature ranges.

Polyethylene Glycol Coated Magnetic Nanoparticles: Hybrid Nanofluid Formulation, Properties and Drug Delivery Prospects

Magnetic nanoparticles (MNPs) are widely used materials for biomedical applications owing to their intriguing chemical, biological and magnetic properties. The evolution of MNP based biomedical applications (such as hyperthermia treatment and drug delivery) could be advanced using magnetic nanofluids (MNFs) designed with a biocompatible surface coating strategy. This study presents the first report on the drug loading/release capability of MNF formulated with methoxy polyethylene glycol (referred to as PEG) coated MNP in aqueous (phosphate buffer) fluid. We have selected MNPs (NiFe₂O4, CoFe₂O4 and Fe₃O₄) coated with PEG for MNF formulation and evaluated the loading/release efficacy of doxorubicin (DOX), an anticancer drug. We have presented in detail the drug loading capacity and the time-dependent cumulative drug release of DOX from PEG-coated MNPs based MNFs. Specifically, we have selected three different MNPs (NiFe₂O₄, CoFe₂O₄ and Fe₃O₄) coated with PEG for the MNFs and compared their variance in the loading/release efficacy of DOX, through experimental results fitting into mathematical models. DOX loading takes the order in the MNFs as CoFe₂O₄ > NiFe₂O₄ > Fe₃O₄. Various drug release models were suggested and evaluated for the individual MNP based NFs. While the non-Fickian diffusion (anomalous) model fits for DOX release from PEG coated CoFe₂O₄, PEG coated NiFe₂O₄ NF follows zero-order kinetics with a slow drug release rate of 1.33% of DOX per minute. On the other hand, PEG coated NiFe₂O₄ follows zero-order DOX release. Besides, several thermophysical properties and magnetic susceptibility of the MNFs of different concentrations have been studied by dispersing the MNPs (NiFe₂O₄, CoFe₂O₄ and Fe₃O₄) in the base fluid at 300 K under ultrasonication. This report on the DOX loading/release capability of MNF will set a new paradigm in view that MNF can resolve problems related to the self-heating of drug carriers during mild laser treatment with its thermal conducting properties.