Preparation of stable colloidal dispersion of surface modified Fe3O4 nanoparticles for magnetic heating applications

The effect of surface modification on enhancing the magnetic heating behavior of magnetic nano fluids were investigated, for this purpose Fe3O4 nanoparticles were synthesized using co-precipitation method and surface modification was done using citric acid, ascorbic acid, tetraethyl orthosilicate (TEOS), polyvinyl alcohol (PVA) and polyethylene glycol (PEG). Experimental heating tests using AC magnetic field were done in the frequency of 100 kHz and different magnetic field (H) intensities. Theoretically the specific absorption rate (SAR) in magnetic nano fluids is independent of nanoparticles concentration but the experimental results showed different behavior. The theoretical SAR value @ H = 12kA.m-1 for Nano fluids containing bare Fe3O4 nanoparticles was 11.5 W/g but in experimental tests the obtained value was 9.72 W/g for nano fluid containing 20,000 ppm of dispersed nanoparticles. The experimental SAR calculation was repeated for sample containing 10,000 ppm of nanoparticles and the results showed increase in experimental SAR that is an evidence of nanoparticles agglomeration in higher concentrations. The surface modification has improved the dispersion ability of the nanoparticles. The Ratio of SAR, experimental, 20000ppm to SAR, experimental, 10000ppm was 0.85 for bare Fe3O4 nanoparticles dispersion but in case of surface modified nanoparticles this ratio has increased up to 0.98 that shows lower agglomeration of nanoparticles as a result of surface modification, although on the other hand the surface modification agents were magnetically passive and so it is expected that in constant concentration the SAR for bare Fe3O4 nanoparticles to be higher than this variable for surface modified nanoparticles. At lower concentrations the dispersions containing bare Fe3O4 nanoparticles showed higher SAR values but at higher concentrations the surface modified Fe3O4 nanoparticles showed better results although the active agent amount was lower at them. Finally, it should be noted that the nanoparticles that were surface modified using polymeric agents showed the highest decrease in experimental SAR amounts comparing theoretical results that was because of the large molecules of polymers comparing other implemented surface modification agents.

Magnetic induction heating and drug release properties of magnetic carbon nanotubes

AIM

The use of magnetic carbon nanotubes for multi-modal cancer treatment, incorporating both hyperthermia and drug delivery functions, has drawn substantial interest. Yet, the present method of regulating hyperthermia temperature involves manually adjusting the magnetic field intensity, adding to the complexity and difficulty of clinical applications. This study seeks to design novel magnetic carbon nanotubes capable of self-temperature regulation, and investigate their drug loading and release characteristics.

METHODS

Using the co-precipitation method, we synthesized magnetic carbon nanotubes with a Curie temperature of 43 °C. A comprehensive investigation was conducted to analyze their morphology, crystal structure, and magnetic characteristics. To enhance their functionality, chitosan and sodium alginate modifications were introduced, enabling the loading of the antitumor drug doxorubicin hydrochloride (DOX) into these magnetic carbon nanotubes. Subsequently, the loading and release properties of DOX were investigated within the modified magnetic nanotubes.

RESULTS

Under alternating magnetic field, magnetic carbon nanotubes exhibit self-regulating properties by undergoing a magnetic phase transition, maintaining temperatures around 43 °C as required for hyperthermia. On the other hand, during magnetic induction heating, the release percentage of DOX reached 23.5% within 2 h and 71.7% within 70 h at tumor pH conditions, indicating their potential for sustained drug release.

CONCLUSIONS

The prepared magnetic carbon nanotubes can effectively regulate the temperature during hyperthermia treatment while ensuring controlled drug release, which presents a promising method for preparing nanomaterials that synergistically enhance magnetic hyperthermia and chemotherapy drugs.

Physical mechanisms of emerging neuromodulation modalities

One of the ultimate goals of neurostimulation field is to design materials, devices and systems that can simultaneously achieve safe, effective and tether-free operation. For that, understanding the working mechanisms and potential applicability of neurostimulation techniques is important to develop noninvasive, enhanced, and multi-modal control of neural activity. Here, we review direct and transduction-based neurostimulation techniques by discussing their interaction mechanisms with neurons via electrical, mechanical, and thermal means. We show how each technique targets modulation of specific ion channels (e.g. voltage-gated, mechanosensitive, heat-sensitive) by exploiting fundamental wave properties (e.g. interference) or engineering nanomaterial-based systems for efficient energy transduction. Overall, our review provides a detailed mechanistic understanding of neurostimulation techniques together with their applications toin vitro, in vivo, and translational studies to guide the researchers toward developing more advanced systems in terms of noninvasiveness, spatiotemporal resolution, and clinical applicability.

A rationale for the rapid extraction of ultra-low-level uranyl ions in simulated bioassays regulated by Mn-dopants over magnetic nanoparticles

Although the sorption of uranyl ions and other heavy metal ions over magnetic nanoparticles is well reported, the parameters governing the sorption process over the magnetic nanoparticles have not been clearly enumerated. However, to increase the efficiency of the sorption over the surface of these magnetic nanoparticles, it is essential to understand the different structural parameters that are involved in the sorption process. The sorption of uranyl ions and other competitive ions in simulated urine samples at different pH was effectively accomplished over magnetic nanoparticles of Fe₃O₄ (MNPs) and Mn-doped Fe₃O₄ (Mn-MNPs). The MNPs and Mn-MNPs were synthesized using an easily modified co-precipitation method and were thoroughly characterised using several techniques, such as XRD, HRTEM, SEM, zeta potential, and XPS. The substitutional doping of Mn (1 to 5 at%) in the Fe₃O₄ lattice (Mn-MNPs) showed better sorption ability as compared to that of MNPs. The sorption properties of these nanoparticles were mainly correlated with the different structural parameters to understand the roles of surface charge and different morphological parameters. The interaction centres over the surface of MNPs with the uranyl ions were designated and the effects of ionic interactions with uranyl ions for these sites were calculated. Extensive XPS, ab initio calculations and zeta potential studies have provided deep insights into the different aspects that play key roles in the sorption process. These materials showed one of the best K_d values (∼3 × 10⁶ cm³) in a neutral medium with very low t_1/2 values (∼0.9 min). The fast sorption kinetics (very low t_1/2) makes them amongst the best sorption materials for uranyl ions and optimal for the quantification of ultra-low-level uranyl ions in simulated bioassays.

Greener design and characterization of biochar/Fe3O4@SiO2-Ag magnetic nanocomposite as efficient catalyst for synthesis of bioactive benzylpyrazolyl coumarin derivatives

The study aimed to develop an efficient catalyst, biochar/Fe₃O₄@SiO₂-Ag magnetic nanocomposite, to synthesize bioactive benzylpyrazolyl coumarin derivatives through a one-pot multicomponent reaction. The catalyst was prepared using Ag nanoparticles synthesized with Lawsonia inermis leaf extract and carbon-based biochar obtained through pyrolysis of Eucalyptus globulus bark. The nanocomposite contained a silica-based interlayer, highly dispersed Ag nanoparticles, and a central magnetite core, which responded well to external fields. The biochar/Fe₃O₄@SiO₂-Ag nanocomposite showed excellent catalytic activity and could be easily recovered using an external magnet and reused five times without significant loss of performance. The resulting products were tested for antimicrobial activity and showed significant activity against various microorganisms.

Phase Change Thermal Storage Materials for Interdisciplinary Applications

Functional phase change materials (PCMs) capable of reversibly storing and releasing tremendous thermal energy during the isothermal phase change process have recently received tremendous attention in interdisciplinary applications. The smart integration of PCMs with functional supporting materials enables multiple cutting-edge interdisciplinary applications, including optical, electrical, magnetic, acoustic, medical, mechanical, and catalytic disciplines etc. Herein, we systematically discuss thermal storage mechanism, thermal transfer mechanism, and energy conversion mechanism, and summarize the state-of-the-art advances in interdisciplinary applications of PCMs. In particular, the applications of PCMs in acoustic, mechanical, and catalytic disciplines are still in their infancy. Simultaneously, in-depth insights into the correlations between microscopic structures and thermophysical properties of composite PCMs are revealed. Finally, current challenges and future prospects are also highlighted according to the up-to-date interdisciplinary applications of PCMs. This review aims to arouse broad research interest in the interdisciplinary community and provide constructive references for exploring next generation advanced multifunctional PCMs for interdisciplinary applications, thereby facilitating their major breakthroughs in both fundamental researches and commercial applications.

Assessing the Heat Generation and Self-Heating Mechanism of Superparamagnetic Fe3O4 Nanoparticles for Magnetic Hyperthermia Application: The Effects of Concentration, Frequency, and Magnetic Field

Magnetite nanoparticles (MNPs) exhibit favorable heating responses under magnetic excitation, which makes them particularly suited for various hyperthermia applications. Herein, we report the detailed self-heating mechanisms of MNPs prepared via the Ko-precipitation Hydrolytic Basic (KHB) methodology. The as-prepared MNPs were fully characterized using various spectroscopic techniques including transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and vibrating sample magnetometry (VSM). MNPs exhibited stable 15 nm quasi-spherical small-sized particles, pure crystalline cubic Fe₃O₄ phases, high saturation magnetizations (Ms = ~40 emu·g^-1), and superparamagnetic behavior. In response to alternating magnetic fields (AMFs), these MNPs displayed excellent self-heating efficiencies with distinctive heating responses, even when minimal doses of MNPs were used. Heating efficacies and specific absorption rate (SAR) values as functions of concentration, frequency, and amplitude were systematically investigated. Remarkably, within only a few minutes, MNPs (2.5 mg/mL) showed a rapid dissipation of heat energy, giving a maximum intrinsic loss power (ILP) of 4.29 nHm²/kg and a SAR of 261 W/g. Hyperthermia temperatures were rapidly reached in as early as 3 min and could rise up to 80 °C. In addition, Rietveld refinement, Langevin, and linear response theory (LRT) models were studied to further assess the magnetic and heating mechanisms. The LRT model was used to determine the Néel relaxation time (τ_R = 5.41 × 10^-7 s), which was compared to the Brownian relation time value (τ_B = 11 × 10^-7 s), showing that both mechanisms are responsible for heat dissipated by the MNPs. Finally, the cytotoxicity assay was conducted on aqueous dispersions of MNPs, indicating their biocompatibility and low toxicity. Our results strongly suggest that the as-prepared Fe₃O₄ MNPs are promising vehicles for potential magnetically triggered biomedical hyperthermia applications.

Improvement of Hyperthermia Properties of Iron Oxide Nanoparticles by Surface Coating

Magnetic hyperthermia is an oncological therapy that exploits magnetic nanoparticles activated by radiofrequency magnetic fields to produce a controlled temperature increase in a diseased tissue. The specific loss power (SLP) of magnetic nanoparticles or the capability to release heat can be improved using surface treatments, which can reduce agglomeration effects, thus impacting on local magnetostatic interactions. In this work, Fe₃O₄ nanoparticles are synthesized via a coprecipitation reaction and fully characterized in terms of structural, morphological, dimensional, magnetic, and hyperthermia properties (under the Hergt-Dutz limit). Different types of surface coatings are tested, comparing their impact on the heating efficacy and colloidal stability, resulting that sodium citrate leads to a doubling of the SLP with a substantial improvement in dispersion and stability in solution over time; an SLP value of around 170 W/g is obtained in this case for a 100 kHz and 48 kA/m magnetic field.

Fabrication of Multifunctional Drug Loaded Magnetic Phase Supported Calcium Phosphate Nanoparticle for Local Hyperthermia Combined Drug Delivery and Antibacterial Activity

Magnetic calcium phosphate nanoparticles are biocompatible and have attracted much attention as biomaterials for bone tissue engineering and theranostic applications. In this study, we report the fabrication of a biocompatible magnetic nickel ferrite supported fluorapatite nanoparticle as a bone substitute material with hyperthermia potential using a facile wet precipitation approach. The composition and magnetic properties of the sample were analyzed using X-ray diffraction (XRD) and a vibrating sample magnetometer (VSM). The presence of both magnetic (NiFe₂O₄ and γ-Fe₂O₃) and fluorapatite phases was identified, and the sample exhibited ferromagnetic behavior with saturation magnetization and coercivity of 3.08 emu/g and 109 Oe, respectively. The fabricated sample achieved the hyperthermia temperature of ∼43 °C under tumor mimic conditions (neglecting Brownian relaxation) in 2.67 min, and the specific loss power (SLP) was estimated to be 898 W/g_(Ni+Fe) which is sufficient to prompt irreversible cell apoptosis. Biocompatibility of the synthesized nanoparticle was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide tetrazolium (MTT) assay with fibroblast NIH 3T3 and L929 cells. An in vitro drug release experiment was conducted at pH 5 (tumor mimic) and 7.4 (physiological), which revealed a release of 49.8% in the former and 11.6% in the latter pH for 11 days. The prepared sample showed antibacterial activity against S. aureus.

Magnetic nanofluids (Ferrofluids): Recent advances, applications, challenges, and future directions

Impelled by the need to find solutions to new challenges of modern technologies new materials with unique properties are being explored. Among various new materials that emerged over the decades, magnetic fluids exhibiting interesting physiochemical properties (optical, thermal, magnetic, rheological, apparent density, etc.) under a magnetic stimulus have been at the forefront of research. In the initial phase, there has been a fervent scientific curiosity to understand the field-induced intriguing properties of such fluids but later a plethora of technological applications emerged. Magnetic nanofluid, popularly known as ferrofluid, is a colloidal suspension of fine magnetic nanoparticles, has been at the forefront of research because of its magnetically tunable physicochemical properties and applications. Due to their stimuli-responsive behaviour, they have been finding more applications in biology and other engineering disciplines in recent years. Therefore, a critical review of this topic highlighting the necessary background, the potential of this material for emerging technologies, and the latest developments is warranted. This review also provides a summary of various applications, along with the key challenges and future research directions. The first part of the review addresses the different types of magnetic fluids, the genesis of magnetic fluids, their synthesis methodologies, properties, and stabilization techniques are discussed in detail. The second part of the review highlights the applications of magnetic nanofluids and nanoemulsions (as model systems) in probing order-disorder transitions, scattering, diffraction, magnetically reconfigurable internal structures, molecular interaction, and weak forces between colloidal particles, conformational changes of macromolecules at interfaces and polymer-surfactant complexation at the oil-water interface. The last part of the review summarizes the interesting applications of magnetic fluids such as heat transfer, sensors (temperature, pH, urea detection, cations, defect detection sensors), tunable optical filters, removal of dyes, dynamic seals, magnetic hyperthermia-based cancer therapy and other biomedical applications. The applications of magnetic nanofluids in diverse disciplines are growing day by day, yet there are challenges in their practical adaptation as field-worthy or packaged products. This review provides a pedagogical description of magnetic fluids, with the necessary background, key concepts, physics, experimental protocols, design of experiments, challenges and future directions.

Reduced graphene oxide nanosheets decorated with core-shell of Fe3O4-Au nanoparticles for rapid SERS detection and hyperthermia treatment of bacteria

In this study, the core-shell of Fe₃O₄-Au nanoparticles (NPs) were prepared by seeding AuNPs onto Fe₃O₄ NPs modified with poly-ethylenimine (PEI). Later, Fe₃O₄-Au NPs were attached to cationic poly(dimethyldiallylammonium chloride) (PDDA)-modified graphene oxide (GO) nanosheets through in situ self-assembly behaviors, termed as Fe₃O₄-Au@RGO nanocomposites, for surface-enhanced Raman scattering (SERS) detection and hyperthermia treatment of bacteria. The resulting Fe₃O₄-Au@RGO nanocomposites were evaluated systematically by transmission electron microscope, zeta potential, X-ray diffraction, X-ray photoelectron spectroscopy, and vibrating sample magnetometer. It revealed that the core-shell structured Fe₃O₄-Au NPs were dispersed homogeneously on the surface of the GO nanosheets. Furthermore, the rapid SERS detection for small biomolecules and bacteria was conducted by Raman spectroscopy. The results showed that the greatest SERS intensity was fne tuned at the weight ratio of Fe₃O₄-Au/RGO nanosheets was 20/1, displaying the optimal interparticle gap of AuNPs to induce the huge hot-spots effect. The magnetic inductive heating capability of Fe₃O₄-Au@RGO nanocomposites was produced under high frequency magnetic field exposure and can kill high than 90% of the bacteria at 10 min. Hence, the newly developed Fe₃O₄-Au@RGO nanocomposites were demonstrated to be viable for SERS detection of biomolecules and microbes and potential applications for magnetically capturing and hyperthermia treatment of bacteria.

Plasma polymerized functional supermagnetic Fe3O4 nanostructured templates for laccase immobilization: A robust catalytic system for bio-inspired dye degradation

Fe3O4 magnetic nanoparticles, synthesized using co-precipitation method, were epoxy functionalized via plasma polymerization of 2,3-epoxypropylmethacrylate (EPMA) precursor. The EPMA-functionalized Fe3O4 nanoparticles (EPMA-f-MN) were employed as templates for facile, one-step covalent immobilization of laccase enzyme at room temperature. Samples were rigorously characterized by FTIR, TGA, SEM, TEM, XRD techniques, while Mössbauer spectroscopy (MöS) and vibrating sample magnetometry (VSM) confirmed the supermagnetic nature of Fe3O4 nanoparticles. Activities of free and immobilized laccase (ImLac) were assayed by spectrophotometrically monitoring the enzymatic reduction of substrate 2,2-azino-bis(3-ethylthiazoline-6-sulfonate) (ABTS) at 420 nm, corresponding to the λmax of ABTS.+. In addition to possessing higher thermal stability and a broader pH tolerance window compared to free laccase, the supermagnetic property of the Fe3O4 renders the ImLac system conveniently recoverable and recyclable. Practical applicability of ImLac towards catalytic degradation of industrial dyes was also ably demonstrated using Acid Blue 193 (AB 193) as a commercially used model textile dye, which belongs to the family of azo dyes. Over 95% degradation of the dye was achieved within a period of 4 hours. ImLac could be used for more than 10 dye degradation cycles with >90 % of retention in enzyme activity.

Toxicity Analysis of Hybrid Nanodiamond/Fe3O4 Nanoparticles on Allium cepa L

Background and Objective. The study of the toxicity of hybrid nanoparticles is necessary before they are synthesized in the laboratory and used in any particular applications. The toxic behaviour of nanoparticles can cause harm for the living species on the Earth. The production of biocompatible hybrid nanoparticles is important. Hence, this study is aimed at determining that nanodiamond/Fe3O4 hybrid nanoparticles were prepared and used for the toxicity analysis on Allium cepa L. Materials and Methods. The chemicals of hydrochloric acid, nitric acid, FeCl3.6H2O, FeCl2.4H2O, NaCl, and NaOH (Sigma-Aldrich chemicals, USA) were utilized in this study. A statistical analysis was performed on the results with a prevalence of $p<0.05$ . Results. A novel ND/Fe3O4 nanocomposite material was successfully synthesized by the in-situ method and characterized by various characterization techniques. The analysis of X-ray diffraction indicated the formation of an ND/Fe3O4 nanocomposite with both participating phases. The saturation magnification of the ND/Fe3O4 nanocomposite is 13.2 emu/g, whereas for a pure Fe3O4 nanomaterial, it is 47 emu/g. The weight rates of ND and Fe3O4 existent in the nanocomposite are 28% and 72%, respectively. From the electrical conductivity analysis, ND/Fe3O4 exhibits conductivity in the order of 27 times more compared to ND. Conclusion. The result implies that the product ND/Fe3O4 has both magnetic and electrical properties. The biocompatibility of the synthesized ND/Fe3O4 material was studied based on the in-vitro method.

Isolation of DNA from Arthrospira platensis and whole blood using magnetic nanoparticles (Fe3O4@OA and Fe3O4@OA@SiO2)

Magnetic nanoparticles (MNPs) provide a fast, cost-effective, and organic-free method for DNA isolation. In this paper, we synthesized MNP coated with oleic acid (Fe3O4@OA) and silica nanoparticles (Fe3O4@OA@SiO2), characterized the properties of MNP using TEM, VSM, and FTIR, and investigated their efficiency in DNA isolation from cyanobacteria. The yield and quality of isolated DNA were evaluated and compared with those from animal blood and those obtained by the silica column or organic solvents. The results showed the successful preparations of Fe3O4@OA and Fe3O4@OA@SiO2 with superparamagnetic behaviors and a mean diameter of 7 nm and 106 nm, respectively. The FTIR spectra of Fe3O4@OA confirmed the bonding of OA to the surface of iron oxide, while those of Fe3O4@OA@SiO2 showed the exposed silanol groups. Although MNPs yielded a lower quantity of DNA compared with phenol/chloroform extraction, they showed the potential  protection of the integrity of DNA against  centrifugal and shear forces. Fe3O4@OA@SiO2 favored more nucleic acid absorption than Fe3O4@OA, producing a 1.2 and 1.6 times greater amount of DNA from Arthrospira platensis and animal blood respectively. The purity of DNA isolated from Arthrospira platensis was also higher than that of animal blood. These findings indicate a new and simple approach for the isolation of DNA from Arthrospira genus.

Graphical Abstract

Polymeric Nanocapsule Enhances the Peroxidase-like Activity of Fe3O4 Nanozyme for Removing Organic Dyes

Peroxidase-like nanozymes are nanoscale materials that can closely mimic the activity of natural peroxidase for a range of oxidation reactions. Surface coating with polymer nanogels has been considered to prevent the aggregation of nanozymes. For a long time, the understanding of polymer coating has been largely limited to its stabilization effect on the nanozyme in aqueous media, while little is known about how polymer coating plays a role in interaction with substrates and primary oxidants to dictate the catalytic process. This work reported a facile sequential modification of Fe3O4 nanoparticles to polyacrylamide coated nanozymes, and as low as 112 mg/L samples with only 5 mg/L Fe3O4 could nearly quantitatively (99%) remove a library of organic dyes with either H2O2 or Na2S2O8 as primary oxidants. The catalytic results and molecular simulation provide both experimental and computational evidence that the hydrogen bonding interaction between the reactant and nanozymes is key for the high local concentration hence catalytic efficiency. We envision that this work, for the first time, provides some insights into the role of polymer coating in enhancing the catalytic activity of nanozyme apart from the well-known water dispersity effect.

Polymer modified magnetic-luminescent nanocomposites for combined optical imaging and magnetic fluid hyperthermia in cancer therapy: analysis of Mn2+ doping for enhanced heating effect, hemocompatibility and biocompatibility

Magnetic Mn_xFe_3-xO₄ nanoparticles and polymer coated magnetic-luminescent Mn_xFe_3-xO₄@(Y,Dy/Eu)VO₄ nanocomposites were prepared to study their comparative heat generation efficiency and biocompatibilities. Cubic crystalline phases were obtained for the nanoparticles and cubic-tetragonal biphasic phases were observed for the nanocomposites. The successful doping of Mn²⁺ was also confirmed by inductively coupled plasma optical emission spectroscopy. The compositions and the surface modification chemistry were confirmed by infrared spectroscopy. The formation of near-spherical and cubic/cuboid nanoparticles was observed from electron microscopy. Comparative analysis of induction heating efficiencies and magnetization values of the synthesized materials was performed for the samples. The samples showed an efficient heating effect under the influence of alternating magnetic field strengths - 3.05 × 10⁶ kA m^-1 s^-1 and 4.58 × 10⁶ kA m^-1 s^-1. A higher Mn²⁺ content was found to possess higher magnetization and perform better in heat generation. The nanocomposites give brilliant color emission on excitation using ultraviolet wavelengths - 300 and 315 nm. Their hydrodynamic radii and zeta potential values indicate good stability of the dispersions. Hemocompatibility studies were carried out to ascertain the effect on red blood cells. The materials were also found to exhibit excellent biocompatibility towards HeLa cell lines. This article will provide a new insight into the use of Mn_xFe_3-xO₄ based nanocomposites for magnetic fluid hyperthermia in cancer therapy.

Fluorinated PEG-PEI Coated Magnetic Nanoparticles for siRNA Delivery and CXCR4 Knockdown

CXC chemokine receptor 4 (CXCR4) is a promising therapeutic target. Previous studies have shown that intracellular delivery of siRNA to knockdown CXCR4 expression in cancer cells is an effective therapeutic strategy. To prepare efficient magnetic nucleic acid carriers, it is now necessary to improve the endocytosis efficiency of PEGylated magnetic nanoparticles. In our work, Heptafluorobutyryl-polyethylene glycol-polyethyleneimine (FPP) was first prepared and then used to coat magnetic nanoparticles (MNPs) to obtain magnetic nanocarriers FPP@MNPs. The materials were characterized by 19 F-Nuclear Magnetic Resonance (NMR), transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), and dynamic light scattering (DLS). The biosecurity of FPP@MNPs was confirmed by cell viability and apoptosis experiments. Cellular uptake of FPP@MNPs and siRNA transfection enhanced by external magnetic fields were detected by fluorescence microscopy, confocal laser microscopy, and flow cytometry. The results show that the cellular uptake efficiency of FPP@MNPs was significantly improved, and transfection efficiency reached more than 90%. The knockdown of CXCR4 on the 4 T1 cell membrane was confirmed by real-time polymerase chain reaction (RT-PCR) and flow cytometry. In conclusion, the fluorinated cationic polymer-coated magnetic nanoparticles FPP@MNPs can be loaded with siRNA to reduce CXCR4 expression as well as be expected to be efficient universal siRNA carriers.

Facile Synthesis of Polyindole/Ni1-x Zn x Fe2O4 (x = 0, 0.5, 1) Nanocomposites and Their Enhanced Microwave Absorption and Shielding Properties

The present work reports the fabrication of polyindole (PIN)/Ni_1-x Zn _x Fe₂O₄ (x = 0, 0.5, 1) nanocomposites as efficient electromagnetic wave absorbers by a facile in situ emulsion polymerization method for the first time. The samples were characterized through Fourier transform infrared spectroscopy, UV-vis spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, high-resolution transmission electron microscopy, and vibrating sample magnetometry. The resulting polyindole/Ni_1-x Zn _x Fe₂O₄ (x = 0, 0.5, 1) nanocomposites offer better synergism among the Ni_1-x Zn _x Fe₂O₄ nanoparticles and PIN matrix, which significantly improved impedance matching. The best impedance matching of Ni_1-x Zn _x Fe₂O₄/polyindole (x = 0, 0.5, 1) nanocomposites was sought out, and the minimum reflection loss of the composites can reach up to -33 dB. The magnetic behavior, complex permittivity, permeability, and microwave absorption properties of polyindole/Ni_1-x Zn _x Fe₂O₄ (x = 0, 0.5, 1) nanocomposites have also been studied. The microwave absorbing characteristics of these composites were investigated in the 8-12 GHz range (X band) and explained based on eddy current, natural and exchange resonance, and dielectric relaxation processes. These results provided a new idea to upgrade the performance of conventional microwave-absorbing materials based on polyindole in the future.

Miniature coiled artificial muscle for wireless soft medical devices

Wireless small-scale soft-bodied devices are capable of precise operation inside confined internal spaces, enabling various minimally invasive medical applications. However, such potential is constrained by the small output force and low work capacity of the current miniature soft actuators. To address this challenge, we report a small-scale soft actuator that harnesses the synergetic interactions between the coiled artificial muscle and radio frequency-magnetic heating. This wirelessly controlled actuator exhibits a large output force (~3.1 N) and high work capacity (3.5 J/g). Combining this actuator with different mechanical designs, its tensile and torsional behaviors can be engineered into different functional devices, such as a suture device, a pair of scissors, a driller, and a clamper. In addition, by assuming a spatially varying magnetization profile, a multilinked coiled muscle can have both magnetic field-induced bending and high contractile force. Such an approach could be used in various future untethered miniature medical devices.

Coating of Magnetite Nanoparticles with Fucoidan to Enhance Magnetic Hyperthermia Efficiency

Magnetic nanoparticles (NP), such as magnetite, have been the subject of research for application in the biomedical field, especially in Magnetic Hyperthermia Therapy (MHT), a promising technique for cancer therapy. NP are often coated with different compounds such as natural or synthetic polymers to protect them from oxidation and enhance their colloidal electrostatic stability while maintaining their thermal efficiency. In this work, the synthesis and characterization of magnetite nanoparticles coated with fucoidan, a biopolymer with recognized biocompatibility and antitumoral activity, is reported. The potential application of NP in MHT was evaluated through the assessment of Specific Loss Power (SLP) under an electromagnetic field amplitude of 14.7 kA m⁻¹ and at 276 kHz. For fucoidan-coated NP, it was obtained SLP values of 100 and 156 W/g, corresponding to an Intrinsic Loss Power (ILP) of 1.7 and 2.6 nHm²kg⁻¹, respectively. These values are, in general, higher than the ones reported in the literature for non-coated magnetite NP or coated with other polymers. Furthermore, in vitro assays showed that fucoidan and fucoidan-coated NP are biocompatible. The particle size (between ca. 6 to 12 nm), heating efficiency, and biocompatibility of fucoidan-coated magnetite NP meet the required criteria for MHT application.

Tetrazol-Cu(i) immobilized on nickel ferrite catalyzed green synthesis of indenopyridopyrimidine derivatives in aqueous media

After the initial study of different protocols in the synthesis of indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidines, herein, a new method is presented using cheaper and more accessible starting materials to produce high-efficiency products. In this protocol, the novel nanocatalyst is very effective in the progression of the reaction and increasing the efficiency. This green approach in aqueous media has several advantages as compared with other methods, such as easier work-up, very mild reaction conditions, reusability of the catalyst, and eco-friendliness. The products of this four-component condensation were evaluated using IR, ¹H NMR, ¹³C NMR spectra, and C. H. N. analyses, and the catalyst structure was confirmed by FT-IR, XRD, SEM, EDX, TGA and VSM techniques.

In this protocol, a novel nanocatalyst was very effective in progression of the reaction and increasing efficiency. This green approach in aqueous media has several advantages compared with the reported methods.

Magnetic Molecularly Imprinted Polymers: Synthesis and Applications in the Selective Extraction of Antibiotics

Recently, magnetic molecularly imprinted polymers (MMIPs) have integrated molecular imprinting technology (MIT) and magnetic separation technology and become a novel material with specific recognition and effective separation of target molecules. Based on their special function, they can be widely used to detect contaminants such as antibiotics. The antibiotic residues in the environment not only cause harm to the balance of the ecosystem but also induce bacterial resistance to specific antibiotics. Given the above consideration, it is especially important to develop sensitive and selective methods for measuring antibiotics in the complex matrix. The combination of MMIPs and conventional analytical methods provides a rapid approach to separate and determine antibiotics residues. This article gives a systematic overview of synthetic approaches of the novel MMIPs materials, briefly introduces their use in sample pretreatment prior to antibiotic detection, and provides a perspective for future research.

Fundamentals to Apply Magnetic Nanoparticles for Hyperthermia Therapy

The activation of magnetic nanoparticles in hyperthermia treatment by an external alternating magnetic field is a promising technique for targeted cancer therapy. The external alternating magnetic field generates heat in the tumor area, which is utilized to kill cancerous cells. Depending on the tumor type and site to be targeted, various types of magnetic nanoparticles, with variable coating materials of different shape and surface charge, have been developed. The tunable physical and chemical properties of magnetic nanoparticles enhance their heating efficiency. Moreover, heating efficiency is directly related with the product values of the applied magnetic field and frequency. Protein corona formation is another important parameter affecting the heating efficiency of MNPs in magnetic hyperthermia. This review provides the basics of magnetic hyperthermia, mechanisms of heat losses, thermal doses for hyperthermia therapy, and strategies to improve heating efficiency. The purpose of this review is to build a bridge between the synthesis/coating of magnetic nanoparticles and their practical application in magnetic hyperthermia.

Insight into the charging-discharging of magnetite electrodes: in situ XAS and DFT study

The structural changes of Fe3O4 nanoparticle electrodes in Li ion batteries during charging-discharging cycles have been investigated using in situ X-ray absorption spectroscopy (XAS). Chemometric methods viz., Principal Component Analysis (PCA) and Multivariate Curve Resolution-Alternate Least Square (MCR-ALS) have been used for analysis of the in situ XANES data during the charge-discharge cycle, which help to identify the various species formed during the lithiation-delithiation of Fe3O4. The concentration variation of the different species has also been determined and the detailed intercalation-conversion mechanism of the Fe3O4 electrodes during the first discharge has been established. Subsequently, the first charge and second discharge cycles were also studied to apprehend the difference in redox reaction between the first discharge and subsequent cycles. The above studies clearly identify the four species involved in the whole intercalation-conversion process of Fe3O4 electrode of a Li ion battery and also indicate the irreversibility of the conversion reaction in subsequent cycles which may be one of the reasons for capacity fading of these electrodes. The above results have also been corroborated with density functional theory (DFT)based ab inito calculations.

Fabrication of thermoresponsive magnetic micelles from amphiphilic poly(phenyl isocyanide) and Fe3O4 nanoparticles for controlled drug release and synergistic thermochemotherapy

The drug-loaded micelles self-assembled from co-poly(phenyl isocyanide), Fe₃O₄ and DOX demonstrated thermoresponsiveness and magnetic hyperthermia for synergistic thermochemotherapy.

One-step synthesis of polyethyleneimine-coated magnetite nanoparticles and their structural, magnetic and power absorption study

Magnetic nanoparticles (NPs) are especially interesting for several biomedical applications due to their chemical surface, especially for targeted cancer imaging and therapeutics. In order to realize these applications, it is important to know their magnetic properties among other complementary properties that help to improve the understanding of the synthesis process. In this work, we report the magnetic properties of polyethyleneimine-coated magnetite (PEI-Fe₃O₄) NPs synthesized by a one-step method via the co-precipitation method and using PEI as a stabilizer. Transmission electron microscopy (TEM) images revealed agglomerated magnetic nanoparticles with an average size of ∼10 nm; meanwhile, the X-ray diffraction (DRX) analysis confirmed a pure magnetite phase. The study of magnetic properties shows a superparamagnetic system with coexistence of non-interacting single NPs with a low blocking temperature (∼35 K) and interacting NPs in the aggregates with a higher blocking temperature (>150 K), in which the interparticle interactions of magnetic cores dominate over surface spin disorder. The interaction between the surface spin-disorder layer and NP core was found to be weak, related to a weak exchange bias effect. A maximum specific loss power (SLP) value of 70 W g⁻¹ was obtained (f = 571 kHz and H = 23.87 kA m⁻¹) indicating that the magnetic response plays a crucial role in determining the heating efficiency for future applications.

Magnetic nanoparticles (NPs) are especially interesting for several biomedical applications due to their chemical surface, especially for targeted cancer imaging and therapeutics.

Immobilization of protein on Fe3O4 nanoparticles for magnetic hyperthermia application

We report a facile approach for the preparation of protein conjugated glutaric acid functionalized Fe₃O₄ magnetic nanoparticles (Pro-Glu-MNPs), having improved colloidal stability and heating efficacy. The Pro-Glu-MNPs were prepared by covalent conjugation of BSA protein onto the surface of glutaric acid functionalized Fe₃O₄ magnetic nanoparticles (Glu-MNPs) obtained through thermal decomposition. XRD and TEM analyses confirmed the formation of crystalline Fe₃O₄ nanoparticles of average size ~5 nm, whereas the conjugation of BSA protein to them was evident from XPS, FTIR, TGA, DLS and zeta-potential measurements. These Pro-Glu-MNPs showed good colloidal stability in different media (water, phosphate buffer saline, cell culture medium) and exhibited room temperature superparamagnetism with good magnetic field responsivity towards the external magnet. The induction heating studies revealed that the heating efficacy of these Pro-Glu-MNPs was strongly reliant on the particle concentration and their stabilizing media. In addition, they showed enhanced heating efficacy over Glu-MNPs as surface passivation by protein offers colloidal stability to them as well as prevents their aggregation under AC magnetic field. Further, Pro-Glu-MNPs are biocompatible towards normal cells and showed substantial cellular internalization in cancerous cells, suggesting their potential application in hyperthermia therapy.

Superhydrophobic Fe3O4/OA Magnetorheological Fluid for Removing Oil Slick from Water Surfaces Effectively and Quickly

Considering the severe impacts on the economic losses caused by oil spills, it is of great significance to develop an oil-absorbent material for removing the oil slick from the water surface effectively. As a new oil-absorbent material, magnetorheological fluid (MRF) has unsinkability, hydrophobicity, and lipophilicity, which could effectively remove the oil slick on the water surface while repelling water. Particularly, the prepared MRF shows a good response to external magnetic field. MRFs show high oil removal capacity in fresh water, deionized water, and salt water with efficiencies up to 94.39, 93.65, and 92.71%, respectively. Besides, Fe₃O₄/OA magnetic nanoparticles (MPs) could be reprepared into MRF by simple treatments. After the fifth cycle, the MRF prepared by the recovered Fe₃O₄/OA MPs still has high oil removal efficiency, and that means the Fe₃O₄/OA MPs has excellent reusability and stability. The method for preparing MRFs provided in this work is simple and effective, and the MRFs have a promising potential for cleaning oil slick.

Synthesis of Core-Shell Magnetic Supramolecular Nanocatalysts based on Amino-Functionalized Calix[4]arenes for the Synthesis of 4H-Chromenes by Ultrasonic Waves

One of the most common phenol-formaldehyde cyclic oligomers from hydroxyalkylation reactions that exhibit supramolecular chemistry are calixarenes. These macrocyclic compounds are qualified to act as synthetic catalysts due to their specific features including being able to form host-guest complexes, having unique structural scaffolds and their relative ease of chemical modifications with a variety of functions on their upper rim and lower rim. Here, a functional magnetic nanocatalyst was designed and synthesized by using a synthetic amino-functionalized calix[4]arene. Its catalytic activity was evaluated in a one-pot synthesis of 2-amino-4H-chromene derivatives. Besides, this novel magnetic nanocatalyst was characterized by spectroscopic and analytical techniques such as FT-IR, EDX, FE-SEM, TEM VSM, XRD analysis.

Preparation, surface functionalization and application of Fe3O4 magnetic nanoparticles

This paper reviews recent developments in the preparation, surface functionalization, and applications of Fe₃O₄ magnetic nanoparticles. Especially, it includes preparation methods (such as electrodeposition, polyol methods, etc.), organic materials (such as polymers, small molecules, surfactants, biomolecules, etc.) or inorganic materials (such as silica, metals, and metal oxidation/sulfide, functionalized coating of carbon surface, graphene, etc.) and its applications (such as magnetic separation, protein fixation, magnetic catalyst, environmental treatment, medical research, etc.). In the end, some existing challenges and possible future trends in the field were discussed.

RF hyperthermia by encapsulated Fe3O4 nanoparticles induces cancer cell death via time-dependent caspase-3 activation

Aim: To explore the optimum temperature for cancer cell death using magnetic hyperthermia (MH), which in turn will affect the mode of cell death. Method: The focus of this study is to improve upon the existing methodology for the synthesis of chitosan encapsulated Fe3O4. MH was done at different temperatures. The cell death pathway was explored using flow cytometry and western blot. Results: Coated Fe3O4 exhibited low cytotoxicity, high stability and heating efficiency. MH at 43°C was the optimum temperature for robust cell death. Cell death pathway suggested that during the initial stages of recovery, apoptosis was the main mode of cell death. While at later stages, major apoptosis and minor necrosis were observed. Conclusion: It is important to find out the long-term effect of hyperthermia treatment on cancer cells and their consequences on surrounding healthy cells.

DABA MNPs: a new and efficient magnetic bifunctional nanocatalyst for the green synthesis of biologically active pyrano[2,3-c]pyrazole and benzylpyrazolyl coumarin derivatives

A new core–shell magnetic silica functionalized with 3,4-diaminobenzoic acid nanocatalyst (Fe₃O₄@SiO₂@PTS-DABA) was prepared and characterized. The Fe₃O₄@SiO₂@PTS-DABA catalyst was applied for the synthesis of dihydropyranopyrazole and benzylpyrazolyl coumarin derivatives.

Boron nitride nanotube@NiFe2O4: a highly efficient system for magnetohyperthermia therapy

Aim: The field of nanotechnology promotes the development of innovative and more effective cancer therapies. This work is aimed to develop a hybrid system that combines the capacity of boron nitride nanotubes (BNNTs) to be internalized by tumor cells and the ability of nickel ferrite nanoparticles to efficiently release heat by induced AC magnetic heating. Materials & methods: The systems studied were characterized by using x-ray diffractometry, transmission electron microscopy, vibrating sample magnetometry and Mössbauer spectroscopy. Results: The ferrite nanoparticles attached to BNNT were able to achieve the required temperatures for magnetohyperthermia therapies. After cellular internalization, AC induced magnetic heating of BNNT@NiFe₂O₄ can kill almost 80% of Hela cells lineage in a single cycle. Conclusion: This system can be a highly efficient magnetohyperthermia agent in cancer therapy.