Shape Of Magnetic Nanoparticles Research Articles

Economic and Accessible Portable Homemade Magnetic Hyperthermia System: Influence of the Shape, Characteristics and Type of Nanoparticles in Its Effectiveness.

Currently, one of the main causes of death in the world is cancer; therefore, it is urgent to obtain a precocious diagnosis, as well as boost research and development of new potential treatments, which should be more efficient and much less invasive for the patient. Magnetic hyperthermia (MH) is an emerging cancer therapy using nanoparticles, which has proved to be effective when combined with chemotherapy, radiotherapy and/or surgery, or even by itself, depending on the type and location of the tumor's cells. This article presents the results obtained by using a previously developed economic homemade hyperthermia device with different types of magnetite nanoparticles, with sizes ranging between 12 ± 5 and 36 ± 11 nm and presenting different shapes (spherical and cubic particles). These magnetic nanoparticles (MNPs) were synthesized by three different methods (co-precipitation, solvothermal and hydrothermal processes), with their final form being naked, or possessing different kinds of covering layers (polyethylene glycol (PEG) or citric acid (CA)). The parameters used to characterize the heating by magnetic hyperthermia, namely the Specific Absorption Rate (SAR) and the intrinsic loss power (ILP), have been obtained by two different methods. Among other results, these experiments allowed for the determination of which synthesized MNPs showed the best performance concerning hyperthermia. From the results, it may be concluded that, as expected, the shape of MNPs is an important factor, as well as the time that the MNPs can remain suspended in solution (which is directly related to the concentration and covering layer of the MNPs). The MNPs that gave the best results in terms of the SAR were the cubic particles covered with PEG, while in terms of total heating the spherical particles covered with citric acid proved to be better.

Feature Matching of Microsecond-Pulsed Magnetic Fields Combined with Fe3O4 Particles for Killing A375 Melanoma Cells.

The combination of magnetic fields and magnetic nanoparticles (MNPs) to kill cancer cells by magneto-mechanical force represents a novel therapy, offering advantages such as non-invasiveness, among others. Pulsed magnetic fields (PMFs) hold promise for application in this therapy due to advantages such as easily adjustable parameters; however, they suffer from the drawback of narrow pulse width. In order to fully exploit the potential of PMFs and MNPs in this therapy, while maximizing therapeutic efficacy within the constraints of the narrow pulse width, a feature-matching theory is proposed, encompassing the matching of three aspects: (1) MNP volume and critical volume of Brownian relaxation, (2) relaxation time and pulse width, and (3) MNP shape and the intermittence of PMF. In the theory, a microsecond-PMF generator was developed, and four kinds of MNPs were selected for in vitro cell experiments. The results demonstrate that the killing rate of the experimental group meeting the requirements of the theory is at least 18% higher than the control group. This validates the accuracy of our theory and provides valuable guidance for the further application of PMFs in this therapy.

Synthesis, characterization, and modeling of gelatin-based magnetic hydrogel beams

Hydrogels are soft materials that can be designed to be responsive to external stimuli such as temperature, pH change, and electric and magnetic fields. Magnetically responsive hydrogels consisting of polymer, water, and magnetic nanoparticles (MNPs) are emerging candidates in biomedical fields due to their remote application. In this work, cobalt ferrite-based MNPs prepared by the auto-combustion method are embedded in gelatin hydrogels. Cobalt ferrite-based magnetic hydrogels (HCFO) having high water content are prepared using the solvent casting method. The effective magnetic properties, such as coercivity and remnant magnetization of the hydrogels, are determined from the magnetization response (m-h curve) obtained through a vibrating sample Magnetometer (VSM). Subsequently, the HCFOs are subjected to uniaxial tensile loading to obtain mechanical properties. The size and shape of MNPs are obtained using X-ray Diffraction (XRD) and scanning electron microscopy (SEM) analysis. Furthermore, the magnetic hydrogel beams (cantilever) have been prepared and subjected to the external magnetic field. A unique phenomenological model has been proposed which can predict the finite deflection of the beam under magnetic loading exploiting the hard magnetic behavior of the HCFO. The proposed model takes into account particle concentration, finite elasticity, and magneto-mechanical coupling. The softness of the hydrogels matrix and hard magnetic properties of the MNPs results in large deflection. Further, the experimental observations and modeling predictions are in good agreement.

3,4-Dihydroxiphenylacetic Acid-Based Universal Coating Technique for Magnetic Nanoparticles Stabilization for Biomedical Applications.

Magnetic nanoparticles based on iron oxide attract researchers' attention due to a wide range of possible applications in biomedicine. As synthesized, most of the magnetic nanoparticles do not form the stable colloidal solutions that are required for the evaluation of their interactions with cells or their efficacy on animal models. For further application in biomedicine, magnetic nanoparticles must be further modified with biocompatible coating. Both the size and shape of magnetic nanoparticles and the chemical composition of the coating have an effect on magnetic nanoparticles' interactions with living objects. Thus, a universal method for magnetic nanoparticles' stabilization in water solutions is needed, regardless of how magnetic nanoparticles were initially synthesized. In this paper, we propose the versatile and highly reproducible ligand exchange technique of coating with 3,4-dihydroxiphenylacetic acid (DOPAC), based on the formation of Fe-O bonds with hydroxyl groups of DOPAC leading to the hydrophilization of the magnetic nanoparticles' surfaces following phase transfer from organic solutions to water. The proposed technique allows for obtaining stable water-colloidal solutions of magnetic nanoparticles with sizes from 21 to 307 nm synthesized by thermal decomposition or coprecipitation techniques. Those stabilized by DOPAC nanoparticles were shown to be efficient in the magnetomechanical actuation of DNA duplexes, drug delivery of doxorubicin to cancer cells, and targeted delivery by conjugation with antibodies. Moreover, the diversity of possible biomedical applications of the resulting nanoparticles was presented. This finding is important in terms of nanoparticle design for various biomedical applications and will reduce nanomedicines manufacturing time, along with difficulties related to comparative studies of magnetic nanoparticles with different magnetic core characteristics.

Ferromagnetic Ni Nanoparticle with Controlled Anisotropy: From Polyhedral to Planar Tetrapods

Liquid phase syntheses mainly yield nanoparticles with compact shapes, such as spheres or cubes. However, controlling not only the size but also the shape of magnetic nanoparticles would enable a fine-tuning of their intrinsic properties, due to the shape anisotropy induced by long-range dipolar interactions. We report here a fairly simple approach based on the reduction of an amidinate complex in the presence of a mixture of long-chains acid and amine to yield ferromagnetic Ni nanoparticles. The formation of stable Ni complexes could be promoted in situ by increasing the acid concentration, thus allowing tuning of the final particle size. While amine could be used as a soft reducing agent, dihydrogen was essential to promote anisotropic shapes. Electron holography combined with micromagnetic simulations showed that the resulting shape anisotropy could impose complex magnetic configurations within planar tetrapods. Regarding the heating efficiency, which directly scales with the magnetic hysteresis loop area, maxima of 100W·g–1 were found for nanoplates and nanorods, opening promising perspectives for magnetically induced catalysis.

The Boundary Between Volume and Surface-Driven Magnetic Properties in Spinel Iron Oxide Nanoparticles

Despite modern preparation techniques offer the opportunity to tailor the composition, size, and shape of magnetic nanoparticles, understanding and hence controlling the magnetic properties of such entities remains a challenging task, due to the complex interplay between the volume-related properties and the phenomena occurring at the particle’s surface. The present work investigates spinel iron oxide nanoparticles as a model system to quantitatively analyze the crossover between the bulk and the surface-dominated magnetic regimes. The magnetic properties of ensembles of nanoparticles with an average size in the range of 5–13 nm are compared. The role of surface anisotropy and the effect of oleic acid, one of the most common and versatile organic coatings, are discussed. The structural and morphological properties are investigated by X-ray diffraction and transmission electron microscopy. The size dependence of the surface contribution to the effective particle anisotropy and the magnetic structure are analyzed by magnetization measurements and in-field Mössbauer spectrometry. The structural data combined with magnetometry and Mössbauer spectrometry analysis are used to shed light on this complex scenario revealing a crossover between volume and surface-driven properties in the range of 5–7 nm.Graphical

Bimagnetic hard/soft and soft/hard ferrite nanocomposites: Structural, magnetic and hyperthermia properties

Recent studies show that the chemical composition and shape of magnetic nanoparticles (NPs) play an important role in their properties. In particular, the bimagnetic NPs display useful and in many cases, more interesting properties than single-phase NPs. In this work, we prepared Fe 3 O 4 and CoFe 2 O 4 cube-like NPs and bimagnetic hard/soft (CoFe 2 O 4 /Fe 3 O 4 ) and soft/hard (Fe 3 O 4 /CoFe 2 O 4 ) nanocomposites (core/coating) using a facile and eco-friendly co-precipitation method that allows the synthesis of the cube-like NPs at temperatures near room temperature. The phase purity and the crystallinity of the NPs with a spinel structure were confirmed by the X-ray diffraction and infrared spectra techniques. Transmission electron microscopy (TEM) images revealed that the NPs have a cubic-like shape with an average dimension of 20 nm. Energy dispersive X-ray analysis, Mössbauer spectroscopy and SQUID magnetic measurements indicated the co-existence of Fe 3 O 4 and CoFe 2 O 4 phases in nanocomposites. In addition, the hysteresis loops exhibited a single-phase behavior in the nanocomposites that indicates there is a good exchange-coupling interaction between the hard and soft magnetic phases. The CoFe 2 O 4 /Fe 3 O 4 nanocomposites presented a larger saturation magnetization than the CoFe 2 O 4 NPs that is effective for their use in magnetic hyperthermia. Finally, we studied the hyperthermia properties of samples in an alternating magnetic field with a frequency of 276 kHz and field amplitude of 13.9 kA/m. Our results showed that magnetic hyperthermia efficiency simultaneously depends on the composition of samples along with magnetic anisotropy and saturation magnetization.

Effect of nanoparticle shape on therapeutic temperature distribution during magnetic hyperthermia

Treatment temperature distribution is a crucial factor for magnetic hyperthermia, since it directly determines the treatment effect related to the apoptosis situation of malignant cells. The shape of magnetic nanoparticles (MNPs) is one of many factors that can affect the treatment temperature during therapy. This paper conducts a comparative study on three different shapes of MNPs by considering the effective area percentage of treatment temperature distribution. The treatment temperature for a proposed model is predicted by solving bio-heat transfer equations, which take the power dissipation of MNPs as the input and consider a temperature-dependent blood perfusion rate in these equations at the same time. The simulation results demonstrate that the treatment temperature distribution can be effectively improved when the temperature-dependent blood perfusion rate is used for the simulation with respect to a constant case. In addition, the MNPs with higher regular shape can lead to a better result than a lower case in the treatment temperature distribution when the same condition is considered for therapy.

Aptamers Increase Biocompatibility and Reduce the Toxicity of Magnetic Nanoparticles Used in Biomedicine.

Aptamer-based approaches are very promising tools in nanomedicine. These small single-stranded DNA or RNA molecules are often used for the effective delivery and increasing biocompatibility of various therapeutic agents. Recently, magnetic nanoparticles (MNPs) have begun to be successfully applied in various fields of biomedicine. The use of MNPs is limited by their potential toxicity, which depends on their biocompatibility. The functionalization of MNPs by ligands increases biocompatibility by changing the charge and shape of MNPs, preventing opsonization, increasing the circulation time of MNPs in the blood, thus shielding iron ions and leading to the accumulation of MNPs only in the necessary organs. Among various ligands, aptamers, which are synthetic analogs of antibodies, turned out to be the most promising for the functionalization of MNPs. This review describes the factors that determine MNPs’ biocompatibility and affect their circulation time in the bloodstream, biodistribution in organs and tissues, and biodegradation. The work also covers the role of the aptamers in increasing MNPs’ biocompatibility and reducing toxicity.

Low-cost sugarcane bagasse and peanut shell magnetic-composites applied in the removal of carbofuran and iprodione pesticides.

In the present study, two agro-industrial wastes, sugarcane bagasse, and peanut shell were employed as support of magnetite nanoparticles for the synthesis of magnetic bio-composites: magnetic sugarcane bagasse (MBO) and magnetic peanut shell (MPSo). The presence of magnetite was verified by Raman spectroscopy. Magnetic nanoparticles shape and size distribution were studied by TEM, while composites morphologies were observed by SEM. Structural characteristics of the pesticides and their possible chemical adsorption on composites were analyzed by FTIR. The removal was carried out by a batch adsorption process, and UV-VIS technique was used for pesticide concentration estimation. Elovich model described better all systems pointing out to a chemical adsorption process occurring. Experimental data isotherms of carbofuran and iprodione can be best explained by more than one mathematical model, but Sip was the ordinary equation in all systems. Maximum adsorption capacities of 175 and 89.3mg/g for carbofuran, and 119 and 2.76mg/g for iprodione, were obtained for MBo and MPSo, respectively.

The Roles of Morphology on the Relaxation Rates of Magnetic Nanoparticles.

The shape of magnetic nanoparticles is of great importance in determining their contrast abilities for magnetic resonance imaging. Various magnetic nanoparticles have been developed to achieve high T1 or T2 relaxivities, but the mechanism on how morphology influences the water proton relaxation process is still unrevealed. Herein we synthesize manganese-doped iron oxide (MnIO) nanoparticles of the same volume with six different shapes and reveal the relationship between morphologies and T1/ T2 relaxation rates. The morphology of magnetic nanoparticles largely determines the effective radius and the gradient of stray field, which in turn affects the transverse relaxation rate. The longitudinal relaxivity has positive correlation with the surface-area-to-volume ratio and the occupancy rate of effective metal ions on exposed surfaces of magnetic nanoparticles. These findings together with the summary of r2/ r1 ratios could help to guide the screening for the optimal shapes of promising T1 or T2 contrast agents. Varying effective radii could be utilized to change negative contrast abilities. The surface-area-to-volume ratio and the amount of effective metal ions on exposed surface are instrumental for tuning positive contrast abilities. These principles could serve as guidelines for design and development of high-performance nanoparticle-based contrast agents.

Dynamic morphogenesis of dendritic structures formation in hen egg white lysozyme fibrils doped with magnetic nanoparticles

In this research, the dynamic process of aggregation that forms microflower morphology in solution of lysozyme amyloid fibrils doped with spherical or spindle-like magnetic nanoparticles during the process of drying as well as their final microstructures were investigated. The prepared lysozyme amyloid fibrils as well as their mixtures with in-lab synthesized magnetic particles, which were prepared by adding the nanoparticles to the fibrils solution after the process of fibrillation was done, were characterized using brightfield trans-illumination-mode optical microscope, atomic force microscopy (AFM) and scanning electron microscope (SEM). Brightfield optical imaging bases upon photoabsorptive property of the fibrils-nanoparticle composites clearly reveals the morphological features in microscale, and additionally, for the in vivo, live action of the time-dependent process of self-assembly of such composites composed of fibrillary structure incorporated with magnetic particles was optically elucidated at ambient temperature. Moreover, while results of AFM reveal delicate and peculiar association of fibrils with magnetic nanoparticles of different shapes, SEM images illustrate a stark difference in fine detailed final morphology of microstructures associated with spherical and spindle-like nanoparticles. Our results indicated that the interaction between fibrils solution and the nanoparticles commence right after mixing, the dynamic process of forming dendritic structure resembling microflower morphology is on the order of minutes, and its final structure is highly dependent on the shape of magnetic nanoparticles.

Magnetic properties of vulcanized natural rubber nanocomposites as a function of the concentration, size and shape of the magnetic fillers

Nickel–zinc ferrites as well as their nanocomposites formed by natural rubber are desirable because they take advantage of the thermal, mechanical and magnetic properties of each component. However, to date, the effect of the size, shape and concentration of the magnetic fillers on the magnetic properties of nanocomposite has not been studied in detail. In this report, we are presenting results about the influence of the geometric characteristic of fillers on the magnetic parameters of nanocomposites. Nickel–zinc ferrite nanopowders (NZF) with stoichiometry Ni0.5Zn0.5Fe2O4 were synthesized by a chemical route named the Modified Polyol Method (MPM) and magnetic nanocomposites were prepared with concentrations between 1 and 10 phr of ferrite nanopowders by thermal compression and hot pressing. From TEM images of ferrite nanopowders aggregates and primary particles in the nanometric scale were identified with aspect ratio different from 1 (r = a/b = 0.99, 0.55 and 0.43). From VSM measurements and particle size, the NZF may be classified as a ferrimagnetic material in a paramagnetic state and the saturation magnetization (MS) was equal to 36.4 emu/g. Performing VSM experiments with different degrees between the sample and the magnetic field, differences up to 9% were identified for the MS indicating a dependence of magnetic parameters on the concentration and shape of particles and aggregates. Magnetization versus time assays were carried out via VSM and two distinct relaxation times were achieved and associated with different populations of size and/or shape for the magnetic fillers. These results point to the possibility of modulation of the magnetic properties of vulcanized natural rubber composites by means of a suitable engineering process to control the concentration, size and shape of magnetic nanoparticles and agglomerates.

Spherical magnetic nanoparticles fabricated by electric explosion of wire

We report the first use of an electrophysical method of electric explosion of wire for preparing magnetic nanoparticles of iron oxide. X-ray diffraction, transmission electron microscopy, magnetization and magnetic resonance measurements were comparatively analyzed. They indicated that the shape of magnetic nanoparticles is close to being spherical. The production order of 100g per hour by this method is advantageous when a large amount of material is needed for applications.